blockstates/<registryname>.json
{
	"forge_marker": 1,
	"defaults": {
		"model": "minecraft:cube_all", // points to assets/minecraft/models/block/cube_all
		"textures": {
			"all": "minecraft:blocks/diamond_block" // cube_all needs a texture called "all", we provide it. This path resolves to assets/minecraft/textures/blocks/diamond_block.
		},
		"transform": "forge:default-block" // Convenience feature by forge, auto transform our block so it will look right in third person mode, etc.
	},
	"variants": {
		"normal": [{}] // This block has no properties and thus just has one in-world variant, "normal". It is left empty because it doesn't change from the defaults defined above. Notice the array enclosing the empty json object. This is important as it tells the forge blockstate deserializer that "normal" is the name of a variant, not the name of a property for which we need to supply values inside (see the forge blockstate specification)
		"inventory": [{}] // Ding ding ding, Forge lets use also use "inventory" to refer here, thus model is inherited from defaults and we're left with one forge blockstate json,  instead of a vanilla one, a block model, and an item model separately.
	}
}