A seat assembly having improved trim appearance is provided as well as a method and mold tool for making the seat assembly. In certain embodiments, the seat assembly has at least one narrow trench having a substantially constant width of up to 5 mm, which provides for better tolerances when installing a trim cover on the cushion and provides improved appearance and comfort. In certain embodiments, the mold tool has at least one tool insert that is configured to create the at least one narrow trench with a substantially constant width in the cushion.