A tooling assembly for use in forming z-channels in a fibrous ceramic preform includes a mandrel having a first plurality of holes extending into a mandrel body, a first subset of the plurality of holes being through-holes extending completely through the mandrel, and a second subset of the holes comprising blind pockets, and a plurality of channels extending longitudinally along the mandrel in a direction orthogonal to the first plurality of holes. The tooling assembly further includes an outer fixture at least partially enclosing the mandrel, the outer fixture including at least one piece comprising a second plurality of holes extending completely through the at least one piece, the second plurality of holes being aligned with respective corresponding ones of the first plurality of holes such that a needle can be inserted through each of the second plurality of holes in the at least one piece and into the respective ones of the first plurality of holes in the mandrel.