This is the part that is optional … depending on how you make your pads……… It is the bottom most layer of fabric – that goes against your underpants. This can be the waterproofing, or can be over the waterproofing. Mostly this is personal preference. How well the pad fits and how well your underpants fit, can contribute to what you may use as backing. For example some people find that as long as the pad snaps firmly around the underpants and the underpants are a snug fit – that a PUL backed pad is fine. Some people prefer to have the extra grip of fleece backing.
You can combine 2 water-resistant fabrics to double the protection, such as using a layer of nylon and a backing of fleece. Wingless pads are often made with slip resistant fabric on the back, because they do not have the wings to help keep the pad in place.
Some people like to have a printed top so they can see the print more often, and some prefer a softer or more natural top, or may like to have a print backing to make the pad more interesting and where it can’t stain.
Commonly pads are backed with:
Printed Cotton/Quilter’s Cotton – for a pretty look to the pad, using quilting cottons or other pretty prints, offers a reasonably slip-resistant backing.
Flannel/flannelette – As with printed cottons, can offer a nice looking back. More slip-resistant than printed cottons. Can look more worn out and pilled, so I wouldn’t recommend using flannel as backing.
PUL – You can make pads with the PUL as the backing. Particularly if you have a printed polyester PUL. It may not slip around as much as you may think (depending on the particular PUL – some brands are slippier than others). The advantage is that without the extra layer of fabric the pad can be thinner and more flexible. Snug fitting underpants should keep it in place, but you may find it is more slippery than cottons.
Corduroy – This is a ridged fabric that can help stop the pad moving around in your underpants. A good choice for wingless pads if you want something natural (Corduroy is a cotton fabric) and that doesn’t add much extra thickness. “Pinwale” cord is a fine ridged version that is still reasonably thin and soft.
Synthetic Fleece – helps water proof/resistance and also helps stop the pad moving, but can feel a little hotter and adds thickness to the pad.
Other choices can be almost anything. Denim, Brocade (can be slippery though), Sherpa… anything you like… Just remember though that the more slippery the backing fabric is, the more likely it is your pad will slip around in your underpants… and a thick backing fabric will add thickness to your pad