I use "Heat Press Batting Together" by Jeanne Harwood Designs. It is a 10 yard roll of fusible 1.5 inch wide cloth tape. You lay the edges of batting together. Press the tape over the two edges. It is made in the USA! www.heatpressbattingtogether.com
It costs $8. I paid $8.50 at my local fabric store. IT IS AWESOME STUFF. Worth every penny and more.
Debi