I have handmade potholder hot pad trivets for a couple years now mainly for sale. I used the InsulBrite insulating fabric from Walmart or JoAnne Fabrics. The shiny side would go towards your cotton print fabric. The otherside goes against the prequilted plain color fabric.
I used the pre-quilted fabric to follow the quilted lines on and to give the potholder an extra layer of batting as well.
Many of my potholder hot pads are currently listed on Ebay. I did sell 8 sets of potholders to one buyer recently. Then I made more potholders so I would have a longer set of postings on Ebay. Hope this helps you out. from, Debbie, Phoenix, AZ.