Cut fabric 7" x 10". I'm using a dressweight cotton ie. poplin.
Bring short ends together and stitch across with a decent seam allowance.
Press seam open flat
Turn raw edges to wrong side (about 0.5")
Turn right side out and press keeping the turned edges as even as possible (they will need to line up when it comes to stitching the picket on) and with the previously stitched seam to one edge (the seam will be on the bottom edge of the pocket)
Stitch across top folded edge of pocket about 0.5" from fold (or a distance appropriate to accomodate the chosen width of elastic) ensuring stitching is secure at both ends.
Insert elastic and securely stitch, back and forth, through the fabric and elastic about 0.5" from the end.
Pull elastic up until pocket measures 4" across the top and secure the end as before. Trim elastic so as the ends are not visible but without being too close to the stitching.
Mark out position of pocket and pin. At this stage you may wish to tack the folded edges (sides) together before pinning if you're not confident with machining the two folded side edges of the pocket accurately together to the lining fabric. Try to keep the pocket on the grain of the fabric and fold a single pleat in the bottom so the bottom is the same width as the top. I've stretched the top of the pocket about 0.25" before pinning so it's not too floppy (any more and it will probably pull in the interfaced lining fabric too much).
Stitch close to the edge around the pocket securing by stitching a few stitches back and forth at beginning and end and keeping folded edges of sides neatly together as you sew. You may wish to tack before completing this last step, particularly if using a slippery fabric.
I hope somebody finds this useful though pink on pink isn't wanting to photograph very well indoors this morning so do say, please, if the pics aren't very clear and I'll remove the post - no point being here otherwise lol!