Your batiks are gorgeous!!
When I make handles, I sew 2 - 2 1/2" strips, plus one strip of batting of your choice. The 2 fabrics are right sides together and the batting on the bottom. Sew all the way down both sides. To turn the handles, I use a 4" very large safety pin (blanket pin) from Joann's. Pin one edge, stick it through the hole, and start pushing and gathering until you can pull the safety pin through the other end. Iron flat, stitch 1/8" from each side. They always turn out great! Good luck with your bags. What a great thing you are doing.