I bought a roll of sheep and goat fencing with 4" squares so I could stick my hand through as needed.
I heard that in your country they build houses out of cardboard, maybe my advice won't work in the US and you don't sell it.)))
I use a net for the trellis, which is used when building a normal brick house, after that, so that the walls are even from the inside or outside, we do the plaster, so that the plaster doesn't fall off, first the net is nailed to the wall. This net is sold in any hardware store. It looks like this
here
Only the mesh should not be chain-link, but welded, galvanized. I take 2 mm thick, 1.5 is possible. The cell size is 5x5 cm. Ty correctly said that fingers should be able to stick through.