Now that both of the side pieces are in I was able to attach the cuff (as it is a toile I only have to do one). I did the left leg as this is the one closest to what they will actually be like.
First I created my pattern by doubling the length of the elastic (which I found out by measuring the width of the ankle) and doubling the width of the elastic so that it would create a tube.
Then I sewed to to ends together using 1.5cm seam allowance and leaving a gap making sure that it stoped before the fold line.
Then I folded it along the fold line (wrong side to wrong side) and sewed a 1.5cm seam allowance allong the top edge.
Then I threaded the elastic through.
After this I closed the gap using a line of stitching that was close to the edge.
I then attached this to the bottom of the trousers using 1.5cm seam allowance.
What do you think?