I have the bag with the root cuttings laid right under the lights. My space is limited so I have all my bags with root cuttings laid out on top of pots where there are no plants growing (example is on top of pots with Nepenthes, where the Nep is growing on the far side of the pot, the bags are laid in the vacant space). I don't do anything special when cutting the roots. I try to cut them where they are about one inch or so in length. I try to avoid burying the roots, but it really doesn't matter. I've had other species of drosera grow their leaves all the way through the moss to reach the light.