An assembly and method for infusing composite material with liquid resin to form a composite part with a smooth outer mold line (OML) surface and a complex inner mold line (IML) surface. The method may include placing a flow media into a deepest tier of a two-tiered recess in a rigid tool, placing a perforated caul sheet into a shallowest tier of the two-tiered recess, and placing uninfused composite material over the perforated caul sheet. Next, the method may include placing an impermeable membrane over the composite material and sealing the impermeable membrane to the rigid tool. Finally, the method may include vacuuming air from a vacuum port of the impermeable membrane to compress the impermeable membrane toward the composite material and the rigid tool, thus pull liquid resin from a resin reservoir, through the flow media, through the perforations of the caul sheet, and throughout the composite material.