I sell die cut appliques and have for year..but I do not fuse mine to the paper backed stuff unless the customer wants it...
most don't like that "stiff" feel...
the ones in keepsake have the fusible on them already..so stiff is what you get!
when you do iron them down, you peel the paper off and place the fusible side down on your "washed" fabric! If you do not wash it, it might not stick properly!
THEN you place a Teflon pressing sheet over it before you put iron on it..this keeps your iron clean should any fusible sneak out where the iron can touch it!
you must then stitch around the applique to keep it permanently in place.