Step One: Cutting and stacking the fabric
Cut your printed canvas in 2 rectangles of 40″ X 50″.
Cut the plain canvas in 1 rectangle of 40″ X 50″.
You want to stack the fabric rectangles with print sides facing out and the plain canvas sandwiched in between.
Step Two: Stitching the rows
Sew stitching lines across the narrower part of the rectangle every 1/2″. At the end, I had 100 rows. This can take some time but is fantastic practice for you to get very comfortable with your sewing machine.
Step Three: Feeding the cord
This part is tricky because you will have to find the best way to feed the cord through all these rows, 50 in total. I'm using a darning needle and have wrapped fairly thick thread to the end of the rope and sewn a couple of stitches with a cross stitch needle. Now I will start passing the cord through the rows.
Feed the cord every other row. In total 50 rows. Stay between the same layer of printed and plain canvas. This will give the mat two distinctive sides. One with higher ridges from the cord and one with slightly lower.
Leave about one inch sticking out the side on each run to secure the cord. You can also decide if you want to leave the cord loops showing for decoration purposes. If you don't, there's no need to keep the cord as one long piece which can be difficult to manage and feed all the way through the mat on each turn. You can just go a couple of turns and start with a new section of cord.
I'm sure some readers will come up with easier ways to do this, so please share your ideas in the comments below.
After you have fed the cord in all 50 rows sew around the mat at 1/4″ from the edge. This to join all the edges and secure very firmly the cords. If you don't want the cords as decoration (I didn't), cut off the ends that stick out of the mat.