Custom Block Placement System

I've previously used Armor Stands, was told by Bhex a minecraft datapacker that you can use a command block fill method and that's great, but what item do I use for the base to let you right click and place? I want the blocks to not be placeable in weird spots like is allowed by item frames, but also not be limited to 2 tall spaces like armor stands. Would a player head method with a fake skull owner data field thats then filled work? Whats the best method in 1.21.2