This is to be a multi-level railway, with different terrain heights. The South Downs are, after all, hills! This is being done in a small way, with no massive structures, but nevertheless I've had to learn the basics. I have never made a model railway before, so this is all new. I purchased "The Scenery Manual" from the Woodland Scenics range to get ideas of what to do.
Clanfield station is a fictitious station set at the top of the South Downs. Hills in the vicinity, and rising trackwork, might then be expected. So far all I had was plywood bases for the track areas, and gaps in between; and there is a need to separate Clanfield from Petersfield station behind it. Throw in a reverse loop emerging from the fiddle yard behind Clanfield, that joins the main line some way down, and there were several objects to "hide" from each other.
The solution to separate Clanfield from Petersfield was to put a hill between the two. There is a local landmark in Clanfield - "Windmill Hill" which has a working windmill on top. The model would do the same. The hill conveniently covers the reverse loop track: BUT I have a rule that any track must be accessible for maintenance; so the hill would need to be removable.
Once the plywood "edges" for the higher ground were complete, the cuttings to the lower levels needed to be sculpted. I used the method described in the Woodland Scenics manual: create the terrain shape with screwed up newspaper, then cover with "modroc" bandage.
Getting the newspaper right wasn't difficult. I used masking tape to hold it in place, with enough at the tops and bottoms not covered in masking tape that the plaster impregnated bandage had a hope of sticking. The edges for the cutting were done first, then the hill was covered.