I make them a variety of ways (for my own use) because we seem to like different thicknesses for different things.
I use one of three setups:
Thin - layer of insul-brite only
Medium - layer of insul-brite and one layer of cotton batt
Thick - layer of insul-brite sandwiched between 2 layers of cotton batt (3 batting layers total)
The thin ones are great for wrapping around a bowl out of the microwave that is only a "little" too hot for bare hands - I make these ones larger than usual and they can also easily be folded in half if a thicker potholder is needed. These get the MOST use in my house.
The medium ones are good all-around all purpose potholders and also serve well as trivets.
The thick ones get the least use, I use them for things coming out of the broiler and also as trivets sometimes.