A method of staging a tissue sample cassette, including a cassette body and a lid, from an upper position in a frame used during a tissue embedding process to a lower position in the frame. The method comprises coupling the cassette with the frame such that the cassette is in the upper position and positively stopped at the upper position by first structure on a wall of the frame. The cassette is moved relative to the frame to the lower position by selectively engaging the cassette with a staging mechanism. An external force is applied to the cassette with the staging mechanism in a direction to move the cassette from the upper position toward the lower position. The cassette is retained in the lower position using second structure on the wall of the frame, such that the cassette is exposed for embedding the cassette in an embedding medium and subsequently slicing the tissue sample embedded in the embedding medium.