I recently bought the larger board at Wal-Mart, and I can still iron on it easily. I iron my husband's slacks on it every week.
I just measured the smaller end, and it starts at six inches. Ten inches in it is 13 inches wide, and 20 inches in it is 17 1/2 inches.
Maybe I can't iron as far down on the slacks as on my other board, when I put them on waist band wise, but I am able to iron as much that way as I need to. It may depend on the size of the slacks. My husband wears 36x 30.