You can absolutely make your own black garlic.
All that is required is to have the garlic in a vaguely air-tight container (preferably individual wrapped or contained) for 30 days at 140°-155°F.
My method, covered at my blog , is to put the garlic in mason jars in my light bulb heated
black garlic oven , which can be made for about $30 and can ferment 12 bulbs easily for about $4 of electricity over 40 days.
With the cost of garlic, glue, aluminum foil and the mason jars, the oven with one recipe is less expensive than an equivalent order would be online.
The first 30 days, the jars are kept sealed in the mason jars, to allow the garlic to ferment properly.
After 30 days, the lids are removed and the heat in the box dehydrates the garlic, leaving a dried out head with shriveled black cloves inside of it.
The flavor is reminiscent of balsamic vinegar and soy sauce, but without the sourness of vinegar or the saltiness of soy sauce.
The oven design is easily doable for anyone of any DIY skill level with access to a hardware store and an Academy (where they sell the Huskee cooler I use for $25).
cooking.stackexchange.com/users/15080/OmniaFaciat
As a chef who has studied black garlic for several years, including visiting China and a manufacturer in Austin to see how large factories make it...the answer is yes you can make it, but it will be nothing like true fine black garlic in any way.
Which is why even chefs in restaurants, such as myself, order their black garlic rather than making it.
It's like saying you can make caviar just by cutting up any old fish who has eggs.
It may look the same but the taste in texture is nothing like the good stuff.
Why?
the steps that can't be done at home.
The first day of making black garlic requires it to be steamed all day.
This is the only way to release the bitterness of regular garlic, a prime component in good black garlic.
Then you canNOT simply cook black garlic on low heat for 30 days as some believe.
It must be alternated in temperature, humidity and more steam and ideally for 40 days straight.
I have come close to making fine black garlic in a process of actually creating my own machinery to mimic the huge batch processes I've seen in China and in one black garlic manufacturer in Austin
but I still order my black garlic because really fine black garlic is exceptional and really fine homemade black garlic is always average to bad
cooking.stackexchange.com/users/15422/Chef E
You can make black garlic by putting garlic 10 days in a rice cooker, on low, and leaving them hanging in a cotton bag for 10 days.
My grandmother is Korean, and this is the way she makes black garlic.
cooking.stackexchange.com/users/8599/yura
I want to share how to make this wonderful fermented black garlic at home.
Buy 15-20 bulbs of organic garlic
(I used organic garlic from California).
In a electrical rice cooker that has cooking and warming settings for 10 cups, place the basket vegetable steamer at the bottom of the rice cooker.
Place the garlic about 15-20 bulbs in an upright position in the rice cooker.
Spray
the garlic with draft beer (I used Asahi Japanese beer) lightly.
Closed the lid and plug the rice cooker, set it at warming.
I recommend keeping the rice cooker outside.
It smells really strong.
I kept mine on the deck under the patio table to keep the snow and rain out.
Leave it alone for 14 days.
DO NOT OPEN PRIOR TO 14 DAYS.
Take the garlic out and place them on a tray and let it dry for 14 days in a cool dark place.
I dried mine in the garage.
Put the garlic in a ziplock bag and store in the refrigerator.
Peel one bulb at a time.
cooking.stackexchange.com/users/17167/Naturalremedy
Thee is a propensity to get better results at fermenting black garlic using hardneck garlic rather than softneck.
Yes I know, what in the world is a neck.well
it is the stem sprouting from the vented of the bulb.
Garlic grown in the Namhae region In Korea seems to be one of the better suited, or at least the one showing the best results.
cooking.stackexchange.com/users/9136/chef oscar lippe
A rice cooker on a low setting would be feasible way to ferment garlic at home.
I don't think it would be necessary to ferment the garlic for the full 40 days, but I'm also not finding any information how the garlic changes day to day.
Looks like you might have to experiment a little.
cooking.stackexchange.com/users/8061/mendota
My wife is Korean and just made a batch of Black Garlic.
She peeled 10 bulbs, put them in a rice cooker, and cooked them on warm for nine (9) days.
Without opening the cooker, unplug it and leave for 11 days.
Then open, drain and peel ASAP.
They're as sweet as you can get.
cooking.stackexchange.com/users/20369/Earl Whitfield
I've seen  black garlic --fermented garlic with a complex flavor--used a number of times on TV cooking shows, but I've never tried it.  The description of the flavor is intriguing.  Is it possible to ferment garlic and make your own black garlic?  What is the process?
Can you make your own black garlic?
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<garlic><fermentation>
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cooking.stackexchange.com/users/10287/Denny Conn
You can make it by keeping the garlic in an airtight container for 10-30 days at 140°-155°F. A rice cooker on a low setting would work for this, but it would not be the same as fine manufactured black garlic. You can make your own garlic in a rice cooker on a low heat for 10 days.
You can make your own garlic. You should ferment it for 30 days at 140-155°F. You can ferment garlic in a rice cooker for 10 days. You can make black garlic but it won't taste the same.