Maybe the attached drawing might help a little?
If the edge of the top measures 60 inches - I would cut the 3 inch border at least 67 inches long. Actually, if I had enough fabric I would cut them 68 inches long - just for a little wiggle room.
I would cut the 6 inch border at least 13 inches longer than the 3 inch border.
If using a 2 inch border - and the top edge was 60 inches, I would cut the strip at least 65 inches long.
I would then cut the 4 inch border at least 9 inches longer that the 2 inch border.
When piecing the borders, I would find the centers of each strip - match the centers - and then pin from the center to the ends. That way I would know that the "overhangs" will be the same on both ends.