Hidden Side Pockets
Hidden side pockets are sewn onto side seam allowances before the side seams are sewn. If you want to add this kind of pocket to your skirt, you can create your own pocket insert pattern.
Making a Pattern
The easiest way to make this pattern is to find a similar pocket in one of your own skirts or dresses and use it to make your pattern. If you don't have anything with this type of pocket, draw your own.
The shape is essentially the same as half a heart. The point of the heart, however, is rounded to form the top of the pocket. For an adult, you probably won't want your pocket to be more than 10″ or 11″ from top to bottom, including seam allowances, or more than 6″ across.
Along the straight side (the center of the “heart”), add a ⅝″ seam allowance. Extend this from the upper edge to as far down the pocket as you want to go. Remember, the seam line has to fit the side seam of your skirt. Don't allow this line to curve outward with the pocket. The farther this seam goes, the more the pocket will be anchored to the seam allowance of the skirt.
Attaching the Pockets
Determine the location for your pockets. Generally, if there is only one pocket, it is on the right side. However, if you are left-handed, you might want to put it on the left side of your skirt. Put them at a comfortable distance below the waist.
Sew the pocket pieces along the seam allowances, right sides together. Make sure the pocket pieces are equal distances from the waist on both the front and the back so they will match when you sew the side seam. Press the seams toward the pocket.
With the right sides together and the pocket pieces extending outward, away from the skirt, pin the side seams and pockets together. Sew the side seam from the waist to the pocket seam and around the pocket, then up to the pocket/skirt seam. Pivot the needle, and sew down the rest of the skirt seam. You might want to topstitch along the front edge of the pocket opening to encourage it to lay forward under your skirt.