This is is a really really slow path to printing these since slicers aren't optimized for grids like this. A better option is:
These grids are meant to be placed over a 64x64 LED matrix panel. They add some isolation to each LED and when combined with a diffuser can create a nice square pixel look.
There are 3 versions, each 6mm tall:
The spacing between the grids is .4 to .5mm so you may need “Detect Thin Walls” depending on your slicer. Each wall will also only be 1 line thick so you may need a calibrated printer for these.
The author hasn't provided the model origin yet.