BB1
I put the splines in before I cut off the top. I do take time with one of the centering rulers to put the spline in the middle of the top (counting for the kerf cutting off the top.
I tried splints method; it did not work for well me. I put self-adhesive sandpaper on the TS and just run the box and lid over that sandpaper to remove any imperfections from the cut.