This is how to make a ghetto-style slope to kicker in your backyard.

Materials: 8-10 sheets of plywood, buy the 1/2 inch stuff as cheap as you can get without holes.
Some bricks to hold the kicker up.
A nice 45 degree hill
Mabye some nails to hold the wood together.

How to build it: Place a sheet of plywood on the slope so that there is room for at least 2 sheets on the slope before you get to the flat. Lay the wood so that the pieces overlap each other so you won't be flying forward. After you get the slope taken care of you need to get one sheet that is perfectly flat. Now for the kicker. Take a sheet of plywood and put in under the flat sheet about 5 or 6 inches and put some bricks under the end to make it raise up. Take the rest of the plywood and lay them (overlapped) down at the end of the kicker for your landing area. Now all you gotta do is put some nails in the plywood on the slope to prevent it from sliding down the hill.