Adding custom items is very simple and only requires very basic resource pack knowledge. For this tutorial, we will be adding a custom sword.
Furniture is created by making a custom item and then changing the translation settings for it.
Translation settings allow you to modify various settings depending on how an item is being used.
If you don’t already have Blockbench (which you likely will, assuming you have completed the requirements), you can download it here: https://www.blockbench.net. Blockbench is an open-source 3d modeling software that has various useful tools for Minecraft models.
To open your model, you can just drag the model JSON into the program.
Once you’re in Blockbench, click on the “Display” tab. Here, you can modify how the model looks when in the player’s hand, on their head, on the floor, in an item frame, or in an inventory GUI.
Most often, furniture is done using invisible item frames. So, you’ll need to modify the translation settings for “Frame”.
What I have done here is rotate the model on the Y-axis by -90 degrees, changed the translation on the Z-axis by -15.5, and scaled the model by 2 on all axis. Now, we can export our model and go back to Minecraft.