Freezer paper pieced means drawing out the design on freezer paper, cutting the various elements of the design up, ironing them onto the different fabrics, cutting the shapes out ... adding your seam allowance as you go ... and then sewing the pieces together while trying to keep the darned templates in place!!!
This means you have ample opportunity to bugger things up ... when you're drawing the templates, when you're cutting them out, when you're cutting the fabric with the seam allowance and when you're sewing the pieces together.
You iron them onto the right sides of the fabric and keep them in place trying to match the hash marks on the templates (like matching notches in a dress pattern) on the two pieces even though they are on the inside of sewn pieces ... Oh yes a veritable funfair to be had!