1) So figure out how much sail you want. Add about 15% for hems and pockets for the mast and battens.
2) Order material. I used 70 Hex XL. 2 yards each of red and lime green. Â
3) Cut out the material. This was tricky for me because I wanted to maximize the sail I could produce in 2 yards of Hex 70 XL. My kayak brands had a detailed pattern available on line.  I used it for my boys’ sail and increased it by 30% for my pro angler kayak.Â
4) Roll hemmed the entire sail.
5) Add a mast stop. Orange duck cloth 5 inches by 8 inches sewn into a tube. Sew one end to the top of the sail 3/4 inch from leading edge. You could skip this step and merely sew the mast pocket in the next step shut but there is a lot of stress and wear on the sail material and within a few sunny weeks a stress hole would emerge.
6) create the mast pocket. Take long leading edge and fold it over 2 inches and sew the entire length. Take the unsewn mast stop and sew it to the opposite side of the mast pocket. Take care not to sew the mast pocket shut.  I double stitched it.
7) Sew the batten pocket. Take a strip of hex 70 2 1/2 inches wide to span your sail from the leading edge to trailing edge add an additional 1 1/2 inches. Hem it, fold over the extra 1 1/2 inches, sew along the edges leaving a small 1 1/2 inch pocket. Sew the strip across the sail on the hemmed edges. Leave the pocket end of the strip unsewn. This is where your batten is slid into place and with light force applied the batten is bent outward and slid into the 1 1/2 inch pocket preventing the batten from coming out. My battens were 36 inches or so long and 1 1/2 inch wide.  I used a wooden yard stick.Â
8) Add two reinforcement patches. One patch 2 x 4 inches of duck folded over the bottom hem near the mast pocket. Used a punch and added a grommet. At the trailing bottom edge I sewed in another reinforcement patch roughly 3 x 3 inches folded over the hem. Used a punch and added a grommet. I used 1/2 inch grommets. Â
9) Put it together. Slide a mast into the sail mast pocket. Ensure the mast stop aligns with the mast. Slide the mast into the mast hole on your kayak. Use 550 cord to tie the mast reinforcement patch to your kayak. Use 550 cord attached to the trailing edge reinforcement patch to control the sail.Â
10) Go Sailing! Â