I take a strip, press it right side up onto gridded fusible interfacing matching the left edge on the line and have the right edge overhang the next line by 1/4" and press. Then add the next strip right side down and stitch. Fold this piece to the next line and press, etc. etc. this is simply the stitch and flip method. The last time I bought the interfacing it had 1 inch squares so you will cut your strips accordingly so you will end up with 2" finished keys. Using this method keeps the border very stable. Here is a good detailed site except she uses non fusible non gridded interfacing. I like the lines to follow!
http://cqmagonline.com/vol08iss01/ar...84/index.shtml