You tape the parchment paper to the bed of your machine. Punch a hole in it for the needle. It provides a slick surface to move the quilt around and over. The acyrilic extension tables have a bit of drag on them and the plastic of the machine throat may also have a drag. I sprayed Silicon spray on my acyrilic extension. I was told many years ago that if your machine throat area is metal then use auto wax spray. If plastic then use teflon spray to make them more slippery.
I couldn't find the teflon backing sheet so got the oven sheet. It works but has a bit of drag but less than the acyrlic.