A 160mm grid/guard : 160mm square with 6" (152mm) central honeycomb grid

The grid pattern is made with prusa slicer.
I made the blank plate, with only 4 fixation holes.
Then in the center i added a cylinder of 6" (152mm), enforcing 2 things :

• No top layers or bottom layers
• honeycomb infill

this causes the central area to become a honeycomb grid pattern.
You can open this file with prusa slicer, and change the infill value to change the grid size (more infill = tighter grid).

You can also change the infill type (grid, lines, triangles, gyroid work well, others might also)

If you need to change the thickness you can alter the base block thickness in prusa slicer by making Z bigger and not touching X and Y.

Print instructions

Open in prusa slicer, adjust settings if need be, select your printer; slice to whatever precision you want (0.2 or 0.3mm fast preset is perfectly fine for such a model), and load the gcode on your printer.
No supports, no brim required.
Whatever material you want works.