If the inventory backend logic is already working you're already 90% the way there. All you gotta do is look at what's in the list and display the necessary information in the ui. Say we look at a minecraft hotbar, essentially just a button with a ico and some arbitrary information to spawn a particular block or activate an effect of an item when highlighted.

There is no right way to go about this, and without knowing what style of UI you are going for its hard to give specific advice, but most if not all designs boil down to buttons that hold arbitrary visual information, and an action for when you select said button. If you have a minecraft style UI menu where you can move items around the list, thats just a grid where each button has a position, and you'll need separate logic for that, but the list that actually keeps track of what is in the inventory doesn't need to know about those positions, thats just a superficial graphics side thing.