My usual solution to this problem is to just twist the opening of the bag and fold it under the loaf of bread when setting it back on the shelf.
Unfortunately my wife isn't convinced that it's an effective way of keeping the bag sealed.
lifehacks.stackexchange.com/users/23311/Josh Withee
As far as quick and easy goes, a good quality bag clip might be what you're looking for.
I don't personally use them on bread bags currently, but I do use them on everything from produce to rice with good results.
They're very easy to release and clip back on, and close the bag when it's flat, rather than twisted, reducing your effort of getting bread out of the bag to three steps (unclip, remove the slice, reclip), as opposed to your current six steps listed.
lifehacks.stackexchange.com/users/22640/Allison C
My grandfather had a good solution to this.
At least, I think it's good.
With the bread inside, give the bag a spin or two, keeping the spun part as close to the loaf as possible.
Stand the bag/loaf on its heel.
Without unspinning, fold the opening of the bag down around the loaf, so that the opening end of the bag is inside out with the front of the loaf inside it.
It is a little neater and more secure than the "spin and tuck" mentioned in another answer, but still requires no additional "hardware."
lifehacks.stackexchange.com/users/24076/fwkb
A one-gallon food storage bag with a plastic "zipper" should do the trick.
Zip open, take out a slice, zip closed.
When you first buy the bread, it will most likely be in a plastic bag.
Remove all the bread from that bag and throw that bag away.
Get 2 one-gallon food storage bags, since a whole loaf won't fit in one bag.
Put half the loaf in each bag and zip them shut.
(You could even store one half of the loaf in the freezer to prolong its freshness.)
lifehacks.stackexchange.com/users/4198/BrettFromLA
Try a heavy-duty clip , like a bulldog clip ( the link is to a picture on thedealsdiscount.com - see picture below).
Scrunch up the end
however you like, and clip it on.
To get your bread, just squeeze the clip to get it off.
lifehacks.stackexchange.com/users/12517/Lawrence
Would it be possible to SAVE one disposable bread bag clip and REUSE it for subsequent bags of bread that come with the undesirable labour-intensive twisty tie.
What a wacky idea.
lifehacks.stackexchange.com/users/4698/Stan
Rapid access versus shelf-life concession.
A purpose-built counter-top storage container called a bread-box is faster for storing and retrieving one or more slices of bread.
The full sliced loaf of bread is placed in the container which has a large front-opening door allowing easy, fast access to one or more slices at your soul discretion.
There is a downside in that the container allows air access greater than would a sealed, close-fitting air-tight plastic bag.
The ambient dry room air will allow the bread to become dry as it ages.
A tighter-fitting box that restricts the amount of airspace will increase the product shelf life at the expense of time and effort to replace the product without damage each time it is opened and closed.
lifehacks.stackexchange.com/users/4698/Stan
A good stout spring style clothes pin works wonders at our home.
We use them to keep a lot of bags closed.
Give the top of the bag a twist, and clip it on!
Unclip it and the bag is as good as open.
lifehacks.stackexchange.com/users/24026/Troy Buerge
There is a thing called a "cord lock" that you might like.
I did a search for it and found it,there are pictures of some.
Get one, tie the ends of a shoelace together.
Put a the looped shoelace through it, pull to tighten.
Store it with the shoelace in the cord lock.
lifehacks.stackexchange.com/users/23758/user23758
It feels so inefficient that when I want to just get a slice of bread I have to completely untwist the tie on the bread bag, untwist the bag, get the slice out, twist up the bag, wrap the twisty-tie around it, and twist it all back together.   The disposable bread bag clips that come on some loaves are a little better, but they're not on all bags and it seems that there should be something even quicker and easier.
Quicker alternative to twisty-tie on a bread bag?
lifehacks.stackexchange.com
<food><storage><fastener>
lifehacks.stackexchange.com/questions/18296
lifehacks.stackexchange.com/users/23311/Josh Withee
A quicker way of sealing a bread bag is to simply use a clip or tie from another bread bag or buy a separate clip. You could also twist the end of the bag and fold it under the loaf to keep it sealed. Other potential solutions include a zip-lock bag or a bread box. The options are to twist and tuck under, use a good quality bag clip, spin the bag and open the top over the loaf, use a food storage bag, resuse a disposable clip, use a bread box, a clothes pin or a shoe lace and cord lock.
A quicker way of sealing a bread bag is to simply use a clip or tie from another bread bag or buy a separate clip. You could also twist the end of the bag and fold it under the loaf to keep it sealed. Other potential solutions include a zip-lock bag or a bread box. You can just twist the opening of the bag and fold it under the loaf of bread when setting it back on the shelf.   One solution would be to save  one disposable bread bag clip and  reuse  it for subsequent bags of bread that come with the undesirable labour-intensive twisty tie.  Failing that you could  buy a good quality bag clip  or just use a clothes pin. A large food storage bag with a plastic "zipper" should do the trick or a "cord lock". Then of course you could use a purpose-built counter-top storage container called a bread-box is faster for storing and retrieving one or more slices of bread.
Suggestions include twisting the opening of the bag and tucking the end underneath, without the tie; a bag clip;  a clothes pin; a cord lock; or a large plastic "zipper" bag. Alternatively, one might save a suitable disposable bag clip and reuse it for subsequent bread bags. You could use a clip, either by buying one or saving one from another loaf of bread. Alternatively, you could simply twist the end of the bag and tuck it under the load of bread. Other options include a cord lock or a zip-lock plastic bag.
Twist the opening and tuck under the loaf. Use a good quality bag clip. Spin the loaf and open the remaining bit around the bag. Use a food storage bag. Save and reuse one disposable bag clip. Use a bread box. Use a clothes pin to seal the bag. Use old shoe lace with a 'cord lock'.
You can just twist the opening of the bag and fold it under the loaf of bread when setting it back on the shelf.    One solution would be to save  one disposable bread bag clip and  reuse  it for subsequent bags of bread that come with the undesirable labour-intensive twisty tie.  Failing that you could  buy a good quality bag clip  or just use a clothes pin. A large food storage bag with a plastic "zipper" should do the trick or a "cord lock". Then of course you could use a purpose-built counter-top storage container called a bread-box is faster for storing and retrieving one or more slices of bread. Cord lock is something you can use
You could simply twist the bag itself and then tuck the opening under the loaf of bread. You could use a clip, either buying one or saving one from a previous loaf of bread. Some options for this include a cord lock or a plastic zip-close bag.