Place 3d Item above block

Hello everyone!

I've made a custom block, and I need that when right clicked with a diamond in hand it places the diamond above the block. How can I do that? Much like the mod Molten Metal where you can put the hot metal above the anvil (that mod was made with Mcreator)

Do I need to make a model in blockbench of a minecraft diamond item and create it in mcreator as a block to be placed above my block? Can I find the model anywhere? Do I need to do something completely different? Help!