Inventory system

I’m trying to make an inventory system for my game but I have no clue how to style it.

I want something like this as a hotbar;

But, my problem is I want to have things like magazines as tools, multiple will take a ton of hot bar space for no reason. So, I need another part of the inventory to show stuff that isn’t immediately in hotbar equipping reach, stuff like magazines. I have no clue how to style this, or where the GUI would go, how would it appear, etc.

Any design help is appreciated.

Just make it like the Minecraft inventory. Make it suit the style of the game.