I use cotton flannel for most of my pads. To make the flannel stretch as far as I can, I sometimes use regular cotton for the wing base. You could use all regular cotton if you like. Just make sure to use a natural fiber like cotton. Stuff like polyester will make you sweat.
Are you not sure what your fabric is made of? You can cut out a small swatch and do a burn test. Synthetic fibers will melt, were as natural fibers burn and leave ash. If you want a exact guide, here is a handy list I stole from someone. I wish I remembered who, so I could credit them.
* Cotton: Burns, but does not melt. It has the odor of burning paper, leaves,
or wood. The residue is a fine, feathery, gray ash.
Most manufactured fibers both burn and melt, and also tend to shrink away
from the flame. Other identifying characteristics include:
Also make sure to use a good quality fabric if you want your pads to last a while. Walmart may be good on price, (flannel for .50 cents a yard!) but you do get what you pay for. All the flannel I bought on the cheap has nearly worn though in less than a year. On the other hand, the stuff I paid more for still looks almost new. Good flannel has a nice even fuzzy nap and a tighter weave. Just as cheaper flannel is the complete opposite, it will also 'pill', which just isn't nice on the tender bits. :D
PUL (POLY URETHANE LAYERS) is a plastic like coated material that is used to prevent leaks. I understand lots of ladies out there can get away with just cloth, I can't. *Shrug* So don't use at your own risk! It can be bought at your local fabric store. If they don't have it in stock, they can order for you. I've tried other plastic type 'waterproofing', and I wasn't too happy with it. It really don't take that much PUL to make a full stash of pads, so it's worth the extra money. (I think my local Joanns sells it for 6$ a yard.) I will admit I've never used the PUL bought in the store. I have another free source for my PUL. No, don't ask. lol.