On a single pair of cargo pants, it's not uncommon to find two or more types of cargo pockets.
The overall structure consists of a pocket with a flap covering the top, but there are many variations to this. Here are three cargo pockets with free sewing patterns for beginners:
Patch Cargo Pocket
The most basic cargo pocket which is commonly found as the rear pocket of pants. It consists of a patch pocket with a flap to cover the top.
It's very easy to construct since the pocket is 2-dimensional. For creating your own garments, this pocket works well as rear pockets or on a jacket where you prefer a pocket that stays flush with your body.
There's a free PDF sewing pattern with video instructions on how to sew your own cargo pants here: https://youtu.be/KepZOZHaJls
3D Cargo Pocket
The 3D cargo pocket, also known as box cargo pocket, has more room for storage because the pocket has depth. With "side walls", these cargo pockets can fit much larger objects.
The depth means the pockets stays in its extended form, bulging out from garments whether it is filled or not.
To sew your own 3D cargo pocket, there's a free PDF sewing pattern and video instructions here: https://youtu.be/smCvW9aopNM
Accordion Cargo Pocket
The Accordion cargo pocket is commonly found on the side of cargo pants. Pleats and folds keep the pocket flat when empty, but it has the ability to expand to hold more items. While this is the most difficult cargo pocket to sew, they provide great range for a pocket.
Find out how to sew your own accordion cargo pocket with a free sewing pattern and instructional video here: https://youtu.be/a1WJtal54dk