It's a good idea to prewash your materials to prevent shrinking of the finished product. You will need two fabric squares for each potholder. Then cut the batting in squares the same size. Next, layer four squares of batting sandwiched between two squares of fabric, with the right sides of fabric facing out. Pin all these layers together.
Basting is an important step to have a nice looking potholder.
Set your sewing machine on zigzag and sew around the edges of the bias tape on all four sides. To make a different size potholder, just change the size of your squares, and adjust the length of the bias tape accordingly. Depending on the stitching options on your machine, you can be quite creative. You can also substitute a pillow binding edge instead of using bias tape around the edge. Then turn it right side out like you would a pillow.