I've used fabric with a specific repeating pattern: these instructions are for general fabrics with hints where appropriate.
Cut six rectangles as shown. My front piece needed extending, but as the bottom will be inside the smaller zipped section I'm happy to bodge. My measurements are based on what fabric I had. If you are matching parts of a design check the pocket piece lines up with the front piece about 2" below the top of the front piece.
I also cut fusible fleece for the three outer pieces and ironed that on.
Gather up pocket lining, one zip, and pocket piece.
Pin them so all top edges align
Stitch through all three layers using a zipper foot (this allows you to get close to the zip teeth). Check whether you need to change your needle position . . . Q: How often do I change needles? A: Every time I break one by trying to stitch into my zipper foot!
Once stitched you can breathe
Fold the fabrics open and top stitch in place
Judge by eye where you think the pocket should be on the front piece. Flip it up and pin 1/4" from the edge of the zip, flip down and see the bottom of the pocket lines up,with the bottom of the front (and your design matches if it needs to). If not repeat until it works!
Stitch using zip foot. Flip into place. This is now your front piece.
Now line up the top of the combined front piece, the top of the second zip and the top of the front lining. (Right sides together, and the front piece right side to the front of the zip) You may prefer to check both zips pull the same way
And stitch. Then flip open and top stitch
Repeat - lining up the back, the zip and the back lining piece, stitching and top stitching
So now it should look like this from the front / outside pieces...
And like this flipped over / inside pieces
I seem to be very good at losing inches (off my fabric, not off my waist!) so now I trim it to size. Take care if you need to trim over a zip - and if your zip is longer than necessary make sure you move the zip pull to the inside
Now move the zip pulls to at least their middles
Arrange the pieces so the lining pieces match up, and the back and front pieces match up (RST). Pop the strap (folded in half) between the back and front pieces just below the main zip, with the raw edges slightly proud of the edges.
Trim the corners, either by eye, or draw around a cup or mug
Pin all round, leaving a 4" gap in the lining. I pin parallel to the edge apart from either side of the gap, that reminds me to stop in the right place
Stitch (going slowly over the Zips). You did move the zip pulls to the centre didn't you? If so you can turn this through (aka give birth) and then stitch the gap closed
Then fill and admire again!
(Then, if you wrote this tutorial, spend ages worrying that you should have used a lighter fabric, or taken better pics, or written it differently . . .)