My backyard is on a very steep slope and somewhat dangerous to walk around in because its very easy to lose your footing and fall. I bought some decorative concrete tiles which I have dug into the slope to create a staircase leading down the slope in the yard. I want to secure the tiles into the hill, so they don't get loose and so they are more permanent. What is the best way to do this? Can I use cement? Can the cement be touching the soil or do I need to lay down a barrier? What is the best cement to use for this purpose?