You might stick a concrete block under the low end of ramp to make the angle less steep,
if they are having any trouble betting up it.(will also help it from rotting against the gruond).
Dirt and/or a chunk of sod from near the chicken yard is what I use at about one week in the brooder.
How long have they been in the coop?
They are about 3 weeks old IIRC...let them go outside into their run.
Dig up a chunk of sod to help them get a hole started.