Armors using whole textures

So i've been seeing some mods that use default the MCreator made layer textures, but then in "textures/models/armor/" they have some armors that are just one png, which is what the armor actually uses for display. My question is, how do i do this same thing?

(The layers in question)
https://imgur.com/SqWTxQl

https://i.imgur.com/iqDQkLB.png

(The single texture that the whole armor uses)

https://i.imgur.com/XeMnhQR.png