If you are not good at DIY and can get 16mm (approx 5/8 inch) melamine boards cut at your local hardware store then these shelf/spacer supports are for you. (Can be used where ever you need some flat storage, like paper etc)

You print 4 of these - one for each corner - remember that all 4 are different and mirrors of each other. Some have nail holes for extra strength on the rear supports. The front ones do not for nicer appearance. All supports have space for screws with a countersunk diameter of about 6.9mm (approx 17/64 inch or ¼ inch)

The size of the boards doesn't matter too much. I had 3 boards cut to 29.5cm Depth x 34cm Width (Thickness 16mm).

These allowed for the following shelf heights:

1. Bottom: approx 68mm
2. First: approx 62mm
3. Second: approx 68mm
4. Third: whatever height you have above it.

These spacers are 247.5mm long, so will fit on a 256mm square bed fine.

If you have a smaller printer that has a build area of 200mm square, then you can print these diagonally on the print bed.

They might fit on a 180mm square bed which has a diagonal size of 254mm (still have to take into account the width of the part)