Step 3: Sew triangles together
Take a triangle from each fabric. With the right sides together, line the two triangles up on the longest edge—the edge where you made the diagonal cut. Pin and sew all the way across.
You should now have two triangles sewn together to form a square.
TIP: If you find it hard to start sewing in the corners, start your seam in the middle and sew to the one corner tip. Then flip the bandana, start your seam in the middle again, and sew to the opposite corner tip.