The felt works well, but it can absorb moisture that will not be good for the wood if the wood is not fully sealed. The compressed cork pad, plastic sheeting, thin rubber strip or string wax work well and will not hold water that can damage the wood. You are almost certainly correct that the clicking noise is coming from the limb/riser interface, which might also be the limb bolts, so make sure to try a little wax or other lubricant on the bolts if the clicking continues after putting the material on the riser pads.
Allan