Another simple design using the Betabrand's pants template and a photoshop software. Not too many layers nor steps to recreate it.
1.Take the Betabrand pants template and duplicate it twice. After you make your duplicates you will need to crop the top half (front view) from the bottom half (back view). Using your second duplicate layer you will need to crop the bottom half (back view) from the top half (front view. This would make it easier to create different looks for both front and back (top and bottom of template).
2. On a duplicate layer of the pants crop away one of the pants leg. Once you do that you crop away the side of the pants leg just leaving the inner portion of the pants leg left. Then you're going to mirror that part. With a duplicate of the pants template underneath the new outline of the bell bottoms just erase on the original outline around the new outline. Duplicate the new outline layer and mirror that onto the other pants leg (right or left depending on the side you started with).
3. Repeat step to for the bottom layer.
4. Create a layer and using the FILL tool, fill in the layer with a color of your choice. After filling in the layer you then would want to change the opacity of that layer making it lighter and the image visible underneath. If you want you can also create/add a texture to the template as well.
5. After applying a color/texture to the template you will have to now clean it up. Using the cropping tool on the color/texture layer try to crop as close to the outline of the template. Then follow up with the eraser tool to get in closer...giving it a cleaner look. . Lastly, you want to merge all the layers in order and delete layers that aren't needed in the finish product then save :)