Methods for forming channels within a substrate include molding a sacrificial component directly into the substrate and igniting the sacrificial component to deflagrate of the sacrificial component and form a channel in the substrate. The sacrificial component can include oxidizing agents such as chlorates, perchlorates, nitrates, dichromates, nitramides, and/or sulfates imbedded in a polymeric matrix, and the oxidizing agents can be 30 wt. % to 80 wt. % of the sacrificial component. The sacrificial component can further include one or more of unoxidized metal powder fuels, flammable gas-filled polymeric bubbles, one or more metallocenes and/or one or more metal oxide particles, one or more polymers with nitroester, nitro, azido, and/or nitramine functional groups, one or more burn rate suppressants such as oxamide, ammonium sulphate, calcium carbonate, calcium phosphate, and ammonium chloride, and non-combustible hollow bubbles and/or inert particles. The polymeric matrix can have a limiting oxygen index of less than about 30.