You'll flip for this dead-centering trick
To quickly cut a perfectly centered 1⁄4 " groove in the edge of a workpiece, set your tablesaw's fence to position the saw blade just to one side of dead center. Cut a kerf, flip the workpiece end-for-end, and cut another kerf. Check the fit of the plywood in the groove and adjust the fence if necessary. If you use a thin-kerf blade (with teeth less than 1⁄8 " wide), you may need to adjust the fence and make a third cut to remove the middle material. Use a featherboard to ensure consistent cuts, and always test your setup in scrap before cutting the actual workpieces.