I just bought a place with a steep sloping front yard too. Unlike you I don't have a lawn planted there. I have one stand of about 4 trees in the center of it and a foundation
flower bed and paving stone walkway. All the rest is dirt. Since I have no intention of trying to mow it ever I'm opting for plants. I plan to plant 9 trees in addition to the group that is there. These will be spaced randomly throughout the space. Leaving at least 20 feet around each tree for planting bushes and
flowers that will appreciate the dappled shade. Along the driveway I'm going to plant dwarf fruit trees. They will get southern exposure from that location and be easy to harvest and prune. I plan to use Irish Moss and other low
growing ground covers that will handle shade between the plantings so I can walk on it to do any weeding and/or plant care.
I've decided on some plants and trees that will add winter interest since I definitely want a 4 season garden to look out on from my bay window. These include a witchazel, a walking stick tree, and a dogwood redtwig clump.