Open ended Gridfinity tools racks.

3x3 through 5x6 grid bases with divisions between 7mm - 39mm

56mm total height

2mm walls all around - Strong enough for a toolbox

Div widths are rounded down, most are +.5mm of extra space.

Material Saving methods--- 

1 - I have had success removing the center grids in my slicer and bridging across. This saves a lot of material 

2 - Depending on your strength needs, you can use your slicer to add triangle/circle holes on the back in between dividers. Same with the Dividers themselves, they do not need to be totally solid.