A slat for use in a covering for an architectural opening is made from a base material of binder and matrix fibers which are formed into a nonwoven material by melting at least a portion of the binder fibers to thermally bond the binder and matrix fibers. A coating of resin is then applied to the thermally bonded base before the composite material is passed through a forming apparatus where the material is heated over a convex support having the desired curvature for the slat and subsequently cooled.