Cut out eight triangles from each fabric. 

Take two triangles from the same fabric, and line them up with right sides together. Sew down the two long sides, leaving the top open. To get a nice point at the bottom, turn the wheel on your sewing machine until the needle is in the fabric at the bottom point of the fabric. Lift the presser foot and pivot the fabric to go up the other side. See the video tutorial at the end of this post to see this in action!

Cut the excess fabric from the top point of the triangle. 

Turn the triangle right side out. Make sure to fully poke the corner out. I use the sharp end of a pair of scissors to really push it out. 

Topstitch around the two long sides of the triangle with a coordinating thread. Again pivot the needle at the bottom to get a nice sharp point. 

Repeat with the other 11 triangles. 

Take a package of extra wide double fold bias tape and finish off the ends. I do this by folding the two ends under about 1/2" and adding a tiny topstitch. This hides the raw edges inside. 

 Lay the bias tape out on a flat work surface. Create a pattern with the triangles. (For example, I did white, red, blue, white, red, blue..) Start 6" from the end of the bias tape and sandwich the tops of the triangles in between. Leave 1/2" to 1" in between each triangle Pin them in place.

Sew down the entire bias tape, being sure to catch the tops of the triangles with the seam.