That is actually a very innovative way to do it - just need to
get the math right to have an equal number of edges on the
remaining parts of the cube to match the circle. Another very
nice method is what I call “fake Boolean”. Make a cube and
tessellate 3 times. Select the inner four polys on two opposite
side and bridge. This will give a square hole. If you want a
round one, re-enforce the outside edges with extract around or
champher and smooth. Those tuts you mentioned - you probably had
a problem squaring off the outer extrusions? Very simple -
select points one side of the outer edges of the extruded
circle, go to properties and under “size” in the X-axis box,
type in 0 and enter. Do the same on the other side, then the top
and bottom using the Y-axis box. Scale to required size and add
thickness. You could also make a circle and a square around it.
Tessellate the square to have an equal number of points as the
circle, use ruled surface to join them and add thickness. There
are just so many ways to achie