Well, there are ton of ways to go about making placement system, there are Tile Based Systems, free placement systems , Pre-defined “block” systems. it’s really up to your personal preference
I would recommend looking at YouTube videos, like this:
(uses module)
Other Sources:
Ego Moose Created a good tutorial on making a placement system: Creating A Furniture Placement System ( same one as mentioned up above, but ported to the devforum)
Side Note: Don’t let that confusing math and stuff deter you( i was confused by it too and i still kind of am), once you understand all of it, its quite cool and resourceful
i made a building system, that you could look through( its a bit messy (code wise) and includes other building mechanics(you might not need), but hopefully it would be of some help) Building System - Roblox