[1.16.5] Adding new player inventory slots, best practice?

[ToastBucket]

I am making a simple backpack mod to extend my knowledge of modding, but after implementing some of the more simple components, (an inventory, the layer renderer, the backpack item), I have run into a brick wall in trying to add a new armor slot to the player, to put the backpack item in. I have examined a few other mods, and they either use the curios api, or mixins, neither of which I am keen to use. (I don't want dependencies for a mod this simple, and I know mixins are a last resort, so I want to avoid them) I know it is possible to add a slot without either, but am totally lost on how to do this, I have heard that capabilities are what should be used, for storing the data, but don't really understand the docs. (or much about capabilities in general lol) I also can't seem to find any information on how to properly render in a new slot for the player inventory, I have seen methods where you would render a second, slot sized gui over the regular inventory, which seems reasonable, if not a bit of a hack, but don't know if it is the right option. I just want advice on what would be the best way to implement something like this, or what best practices I should take into consideration. 

Edited March 4, 2022 by ToastBucket

[ToastBucket]

So, I should just use Curios?