Patio-working on a slope

[newhomeowner]

My husband and I are extending our current concrete slab patio with pavers on all 3 sides. So far it is turning out great. The problems is-on 2 sides of the extension we are working on a slope of about 6 inches from the height of the concrete slab. Using the flex-base system we've laid down gravel rock and sand.
Any suggestions on how to best 'anchor' the 2 sides that will be built up 6 inches higher than the grass? Because of the height the normal edging material is not high enough to hold everything in.
I am considering making a flower garden around the patio; but am curious if just placing dirt around will do it? I am concerned that not holding the patio in place w/ something; eventually the gravel and sand will get loose and wash away.
Any suggestions are appreciated! We are new at this.

[canoebuilder]

You concern is real.
There's 2 ways around it...ONE, to build a small retaining wall creating a step... or TWO... give it a gentle slope and plant grass on it to retard any errosion from the water.
Your idea of a flower planter can be incorperated into the first idea and the 6 inch height is such that I wouldn't worry too much about it falling away.
Gerry