This is a variant of my tunnel block with a flat bottom meant to be used as a baseplate:

• features rabbit clips and sockets to allow multiple basepaltes to be locked together
• features pockets for rubber feet, default setup for 6x2mm feet (0.5mm deep pockets)

These are designed for a desktop grid module that you don't want to accidentally slide around.

Suggested slicer settings:

• split the baseplate itself from the clip sub-object
• the baseplate works well for me using 5% infill (3d honeycomb), 3 top/bottom layers, and no support
• the clip seems best printed with 2 walls, 0 top/bottom layers, and 0% infill; it should be all wall paths

I've also uploaded a 1u-tall version that is just a grid of Z-holes with the same rabbit clip sockets.

Parameterized openscad model for easy customization: https://github.com/jcorbin/gridfinity-risers