I unpicked the side and bottom seams of each bag. Actually, I unpicked one of the lines of stitching at the bottom but decided to cut the waste part (the circle) off next to the line of overlocking because the two layers of fabric were overlocked together.
The pieces I got from the two bags looked like this:
First, I ironed the pieces flat and measured them.
I decided to unpick one end of each handle so I could make two longer handles instead of four short handles. So, I needed to leave the line of stitching in place that goes around the top (red line) and remove the stitching for the handle (blue lines).
I pinned and sewed the two bags together down the sides (green lines), using a sewing machine. This gave me a tube, open at both ends, with the handles at the top.
I pinned the handles together so the side seams were off-centre. Then I sewed along the bottom of the bag between the two side seams (green line).
Complex bit: I folded the bottom corner of the bag at 45° so the bottom seam ran down the centre and one of the side seams went off at right angles to the side. I pinned across the corner and sewed (green line). Then I did the same on the other bottom corner.
When the bag was turned right side out, it looked like this:
Now I decided how long I wanted my handles to be. I ended up overlapping them and stitching them together at each end of the overlap.
I tried to follow the original lines of stitching (not sure that it mattered so much, but I decided that it looked good).
I unpicked a small line of stitching that secured the drawstrings on the original bags:
Then, I tied the two drawstrings together at each end. I used fisherman’s knots. Keeping the drawstrings means I can close up the top of the bag a bit.