This resource Might be helpful! Creating A Furniture Placement System
Also if you would like to look through a building system i made to get a better understanding you can(Warning its not polished and is a bit messy and unorganized ) : Building System - Roblox
Edit: I accidentally linked the wrong version of my building system( i replaced it)
And lastly These are also good tutorials:
If you have any questions i would be glad to help!