Bossone, when shoring up up a steep grade for customers we use one of two methods....First you can take and lay your first row of the biggest rocks out in a line at the deepest point you want them. You may have to seat a few of them to keep them from rolling. After you have done this get some quick crete, mix it up in five gallon buckets , and pour on both the upside hill and the down hill side of the rocks. usually every so often we'll dig a small hole for the Q.C. to fill and act as an anchor after it hardens. Once this is set up you can put rocks and/or gravel against this up to the highest point you want. OR We will cut a bunch of rebar stakes two to three foot long and pound them in to the bank. If you do this every six inches or so then they will hold your bigger rocks in place and you can use this as a back stop for the rest of the rocks. Either way works. The only issue is if you have a solid enough bank and enough clay for option two.