How to crop a triangle shape out of a rectangular shape?

I'm using Photoshop CC to make planner printables and I really want to create one of those flag-style shapes where the triangle is cut out on the end. It's usually referred to as a Bunting Flag or a Pennant Flag. Essentially, it's a rectangle that is missing a triangle shape at the end of it. It's also often used as the shape for bookmarks (like the shape often used to represent a bookmark). I've been using Photoshop for a few weeks while I've been making these printables and I've figured out the basics, I feel like, and I've successfully made things like Chevron patterns where the pattern shape was already sort of preset into the program. I tried drawing the shape using the Line Tool but then I couldn't figure out how to successfully fill in the shape with a color. I also tried putting a rectangle over it at the end of the shape and using the Subtract Top Shape feature under Layers but it would only cut out the triangle portion that was overlaying the rectangle and left the rest of the square that wasn't overlaying the rectangle.

In short, I'm looking for a way to create a banner/flag style custom shape very much like a Bunting or a Pennant flag where it's a rectangle with a triangle cut out at the end (often used as an icon to represent a bookmark) and be able to save it to Photoshop as a custom shape to make it easier to use in the future.