One thing I noticed about alcohol stoves is they tend to be sensitive to cold surfaces, especially cold rocks. These tend to be small, thin-walled aluminum cans with a small amount of fuel. The alcohol has to be warm enough, at least at the surface, to vaporize in n order to sustain a flame. To counteract the heat sink effect of cold surfaces, I carry a small piece of aluminum foil-wrapped corrugated cardboard, usually just about the size of my pot, placing it under my stove. In addition to insulating the pot from its support surface, I protect that surface and get some heat reflected to the pot. This solution is lightweight age cheap, two of my favorite gadget attributes. Unlike foam, the cardboard doesn't melt and i can set the pot onto it for bottom insulation, yhen slip my cozy over the pot to allow the food to finish redhydrating.