1. Cut your strips whatever size you need. For this project I am making 6.5" strips for borders on a quilt. Trim off your selvages.
2. Layout 1 strip, right side up with the short edge on the right side and the rest of the strip going towards the left.
3. Take your second strip and place it right side down perpendicular with the short side lines up with the top and right edge of the bottom strip.
4. I know I try to never ever have to draw a sewing line on the fabric, but with a strip this large it is unavoidable. However with a thinner strip you can use your 1/4" tape line to get the diagonal line to sew on. I like to pin the top and right side of the strips so nothing slips.
5. Put a tiny mark on the top strip where the bottom right part of the bottom strip is. Now draw a line from the top left corner of the top piece to tiny mark you just made. This is your sewing line. I used a dark pen for you to see it, but I usually use one of the blue marking pen that goes away in water.
6. Sew along that line. When you are done unpin and open the seam up to make sure the sides match up.
7. Trim the excess off 1/4" away from the seam.
8. Press the seams open for less bulk and there you go. If you are making a longer piece (such as for binding) keep adding strips in the same way. The bottom strip will be the part you just sewed on and the top strip will be the new one you are adding.