Don't get freaked out by the various pair of pants. As you'll be able to see, I do this a lot! And I love wild prints for my pockets and waistband finishes. If you do this, every time you go to the bathroom all day, you'll be smiling! :P}}
I have taken this from David Page Coffin's book Making Trousers for Men & Women. I can't recommend the book highly enough. Like his book on Shirts, this is the definitive textbook for making trousers. I took his instructions, and wrote them out with pictures so even I can get it right start to finish!
Modify your pattern front side to have a flap that extends past the normal seam allowance. Add the flap along the front side past the seam allowance along the area where your pocket will be. The total width including seam allowance should be 1.25" if you use 1/2" seams. Adjust appropriately for your preferred seam allowance. It should start approximately 1.25" below top of pants including upper seam allowance, and extend approximately 5 to 7 inches long, depending on the size of your hand. Your hand needs to be able to fit through the opening without stretching the pocket opening.
Cut a pocket square approximately 15" wide by 12" long. This can be cut from the fashion fabric, regular cotton pocketing, or any tightly woven cotton. Quilting fabrics work great. You will fold it in half, with the fold towards the pants center front seam. Place the folded pocket square underneath your pants front pattern. The top should be at the top of your pants to be included in the waist seam.
Cut the outer edge of the pocketing to match your pattern hip curve. While you cut the pocketing, you can ignore the flap and just do the pocket the same as the pants would be without the flap.
The total width including seam allowance should be 1.25" if you're using 1/2" seam allowances, or 1 3/8" if you're using 5/8" seam allowances. Again, you want your pockets opening to start approximately 1.25" below top of pants including upper seam allowance, and extend approximately 5 to 7 inches long, depending on the size of your hand. Your hand needs to be able to fit through the opening without stretching the pocket opening. (See photo)
Note: I use 1/2" seam allowances, with an extension of 3/4" extra or 1 1/4". If you are using 5/8" seam allowances, adjust as needed. A 1" extension also works, and will be just a little wider on the interior of your pants where no one can see it.
Cut the clipping lines on the pants front as shown in the diagram. Finish the outside edge of the flap.
Sew front and rear darts.
Make the Pockets
With the right side of your pants front up, position the cut out pants front over the front pocketing. Extend the top of the pocket up to the waist edge of the pants so it will be caught in the waistband seam. Check to be sure your hip curve matches on the pocket and the pants front. The extension should go beyond the curve of the hip by 3/4" to 1". Mark the pocket edges on the pocketing.
Reinforce the pocketing edge only with stay tape adjacent to and abutting the seam line. to keep the pocket edge from stretching when you're wearing the pants. You can either use sew in or fusible stay tape or narrow twill tape.
Fold the extensions over the pocketing (wrong sides together ~ you want the print showing when the pockets are complete!) and zigzag through the pocketing and extension ONLY. Be sure not to catch the pants in this stitching!
Fold the pocketing so it matches up along the seam line with the edge of the pants that will be sewn to the pants back. Position the pocket facing between the layers so it lines up with the side seam, and covers the pocket opening. Zigzag the facing inner edges to the pocketing, leaving about 1" open at the lower side edge so it can be folded out of the way when you stitch the side seams. NOTE: Don't do the outer edges. They will be caught in the side seams.
Topstitch the pocket edge. At this point, I like to fold it again so the inside edge of the pocket is even with the stitching line and topstitching edge is 5/8" inside the seam line for 1/2" seam allowance. You can baste the edges together so they don't shift when you stitch the side front to the side back if you choose to do so.
Baste and stitch the pocket bottom together. I like to pin them together inside out first, stitch the seam, turn them, and topstitch with the raw edges inside the topstitched area. It reinforces the seam and makes it look nice on the inside.
Fun photos of very sedate looking exteriors and fun interiors!
Khaki twill slacks with camo pockets
Grey polished cotton slacks with stars!
and my favorite: Tropical navy wool trouser with circus pockets!
If you decide to make these pockets in your pants, let me know. It's fun to know there are other sewists walking around with sedate pants on the exterior and wild pants on the inside!