So many ways. Have you thought of digging in some good-sized rocks to create pockets of dirt and maybe help prevent erosion? We once used old railroad ties to terrace a slope somewhat. I would also consider planting some low spreading evergreens to hold soil. There are always bricks and all sorts of pavers to use to create steps/paths on the slope. You could also lay down the gardening cloth to hold soil in place. We drive small stakes into the cloth to hold it down, then cut holes for the flowers to go in. Cover it with mulch.
I planted mine in the sides of the incline, choosing things that will grow.
You can also purchase "mats" that have flower seeds imbedded in them. You can attach them with long landscape pins, and water as directed. Treat with Miracle Grow fertilizer. If slope is in need of raking prior to planting, dig yourself "terraces" to facilitate the job.