Hi Kate! I'm no expert but that's what all my boosters are made of and in my opinion they are better than bought ones.
I have 3 layer hourglass shaped boosters and 2 layer square boosters that I fold in half (so effectively 4 layers). I use those at night. I don't use flannel on mine, but if the bamboo is next to her skin I use a micro fleece liner as the bamboo is quite drying on their skin.
HTH.