Yes, a border board will keep the ballast in place, especially with the
slope, and help stabilize the edging 2x2 stones.
I like to use Bend-A-Board, a reddish recycled plastic product, and be sure
to use bendaboard stakes, too. Neither will rot, and will saw, bend, and
screw with no splitting. Usually I use the 1x6 boards, 20 feet long. They
also come in 1x4, 2x4, and other sizes. I place the border so it is just
short of flush with the final stone surface, so the border board basically
disappears, as it should, as it is a below-grade product.
Roger

"Bill Stock" wrote in message
...
I'm installing a shed on some 2x2 patio stones in an 8x10 rectangle. The
ground is not level, being about 4+ inches higher on one side than the
other. I plan to put about 5" on 3/4 gravel and 2" of Limestone screenings
under the patio stones to help with drainage/heaving. But I'm wondering
how much the gravel might migrate if I don't put a border (PT lumber)
around the outside? I did something similar a few years ago with some
penny pavers and marble chips (same gravel base) and I used a PT border to
keep the chips in place. It worked out well then, but I hadn't really
planned to go to the trouble this time. Although with my slope it might be
a good idea.

Any preferences?