Model

Model file

Open BlockBench and create a "Java Block/Item".

Create your model, in this example I'm modelling an ugly minimal modern lamp.

Edit how the model is shown on player hand:

Configure the in-game view

Using armor_stand

You have to select the head icon and then small ArmorStand:

Then you have to shift your model down until it matches the ArmorStand base:

Using item_display

Make sure to specify HEAD in your configuration.

    behaviours:
      furniture:
        entity: item_display
        display_transformation:
          transform: HEAD
        gravity: false
        fixed_rotation: false

You have to select the head icon and then normal ArmorStand.

Then move the model until it's approximately like that. It will be close to the ground. You can later regenerate your pack to preview it in-game and move the model until it's in the correct position.

Using item_frame

Select Frame and Invisible Top. Adjust the model Z Translation (the blue arrow) until it matches the bottom of the white block perfectly.

Export the model

Now let's save the model file into the correct folder, in this case I set this property in the .yml configuration file: model_path: lamp, so you have to save the .json file inside this path: contents/myitems/models/lamp.json.

To achieve this, click on "File" followed by "Export Model" and finally "Export Block/Item Model". In the new window, head over to the path where you want to save your model, give it the correct name and confirm the changes.