Upcycling men's trousers

Recently I decided to make a new backpack purse for myself. I decided to upcycle men's trousers for the lining. The crease of the pant leg is on the straight of grain, and the sides flare from there. I started by cutting the trousers apart at the side and crotch seams. Each piece I was left with was not large enough by itself, but I figured out a way around that.

After cutting the front from the back I pinned it to my carpet. (Taping it to a solid surface floor would work as well.)

Next I pinned a measuring tape to the bottom of the pant leg (shown on the left).

I pinned the tape measure so that it was parallel to the pant crease.

I used a white heat sensitive marker at a few points along the tape measure line.

Next I used my ruler to draw a solid line.

I lay the second half of the pant leg so that the crease marks were parallel, but the leg was oriented in the opposite direction (bottom to top, and top to bottom).

I pinned the second leg down as well.

After verifying that the crease marks were still parallel, I used my ruler to transfer the line to the new piece.

While I was doing that I also marked matching start and stop points on the two parts.

Then I cut both pieces on the white line.

I sewed the two pieces together with a 1/2 inch seam allowance.

I ironed the seam allowance to one side.

I cut down one seam allowance to 1/4 inch.

Then I folded, pinned, and sewed the larger seam allowance around the smaller one.

I now had a piece of fabric that an uneven edge. I aligned my ruler with the crease marks and cut an even edge.

I repeated the process with the second pant leg.

Then I sewed the two pieces of pant leg together at the newly cut edge.

I again ironed the seam allowance to one side.

I followed the steps for binding the seam allowance on this larger piece.

Now I could lay out my pattern piece and cut it from the upcycled trousers - plenty of room!