Custom non full blocks

Hey, ive been toying with datapacks/resource packs recently, and am trying to add a simple custom block. I've got the item_model changed via resource packs. I've followed a quite old tutorial where they use an invisible its frame with the custom item in it, then place a random block over it for collision, which they handle placing and breaking via datapack. The problem i run into is that the item i want to make isnt a full block, aka theres gonna be a random block over my custom placed item, so the solutions I've thought of are either have an invisible block, which idk if its possible, or making a custom model for a block in game. Is that possible? Also if i could be reditected to a written guide or video specifically targetting non full custom blocks I'd appreciate it.