Since I'm working on my gray pants and decided to make a regular quarter pocket instead of an inseam pocket or a patch pocket, I decided to share with you the way I got about drafting and sewing these pockets.
I don't claim to be an expert by any stretch of the imagination, and I'm mostly a self taught sewer, but this is the way I do it, and for me, it's easy, intuitive, and goes rather quickly.
DRAFTING a 3/4 Pocket for your slacks draft
Start with a copy of your basic slacks front draft. Take the front piece, and pin out the darts, with the dart legs going towards the side seam, as if they were sewn.
Because I'm attempting a weight loss program and hope that I will need to take in the side seams on my pants, I've used a larger than normal pocket area of about 1/3 of the distance from the center front seam to the side seam for my pocket depth. Anything from 1/4 to 1/2 of the front is typical for slacks pockets, but for women, quarter pockets are most seen.
Draw in the shape of the pocket you want. I've made mine a bit deeper and wider than I normally would. Mark the grain line on the pocket piece before cutting! Cut the pocket piece off the draft. If you want seam allowances added to your pattern, add them now to each cut edge so you won't forget. You will use the cut off piece as a facing for your pocketing if you make it out of quilting cotton or regular pocketing.
Get a new piece of tissue paper, and trace off the front side piece. You can do any width up to and including the full front width of the pants, or more typically, start at the inside dart and draft from there. Be sure to add the grain line that mimics the pants front.
The next piece of tissue paper will be the back side of the pocket or pocket pouch. I do separate pieces as it takes less fabric and I can use scraps or remnants for the pocketing. Trace off the pocket piece top, center, and bottom lines. Trace the side seam off your front pattern piece. Mark grain lines and add seam allowances if desired. If you prefer, you can just double your tissue paper when you're making the first pocket piece, cut it double, and then cut off the facing piece before adding seam allowances. Note the notch where the pocket piece edge should hit.
Note: These are your pants, so if you prefer, you can use a rectangle with straight bottom and a fold on the interior side of the pocket. I like the rounded pockets a bit better as I feel they produce less lint.
Cut your pocket pieces from your preferred fabric. I like quilting cottons for the cheerful view when my pants are open, but you can use fashion fabric, dedicated pocketing, or even heavy muslin.
Cut your pocket facings from your fashion fabric using the piece you originally cut off the side of the pants front, and being sure to add seam allowances.
Cut the facings out of your fashion fabric if you're using any thing other than fashion fabric for your pocketing.
Sew facing to pocket bag with wrong sides together. Press to set stitches and then set aside. If you haven't done so already, sew darts in front.
Place wrong side of pocket piece to right side of front. You can see where I didn't get my seam allowances exactly the same. I'll fix that when I'm doing the waistband. Stitch along the curved edge, being very careful not to stretch the seam.
If you want to be sure it doesn't bag, you can sew a narrow piece of twill tape to the underside of the seam. (Sew the twill tape to the wrong side of front.) Cut it about 1/4" shorter than the seam, and stretch the twill tape to meet the length of the pocket edge as you're sewing.
Press flat first. Then press seam open. Clip curves. Trim seam allowances. Under stitch.
Turn pocket to inside, and edge stitch and then top stitch the outside edge of the pocket. Press again to to set the stitches. Use clapper if necessary to get it nice and flat.
Now, turn the pieces over and stitch the pocket seam. If the pocket pouch and the pocket seam lines don't match perfectly, that's fairly normal. Once you've stitched the seam and reinforced it with a second line of stitching approximately 1/8' away, you can either serge the bottom or zig zag in a very tight stitch for further reinforcement. Press flat. Baste upper pocket edge to waist seam allowance. You're done!
Finished pockets on Pants Front
If there's something I didn't make clear, drop me a note and I'll see if I can explain more fully.