I baste the quilt top and the batting on the top only before I start to longarm it. The bottom of the quilt top is on one of the rollers so that I can tighten it as appropriate. I was told when I started longarming to baste the sides before quilting but this has caused more problems for me so I don't do that anymore. I just make sure it is straight with the sides every time I roll it and that works for me.