The device that makes operations possible in the compact concepts S4F and CYS is the Staging Traverser. This eliminates an unlimited number of turnouts and tail tracks.
I would make this out of poplar dimensional lumber. Poplar is harder than pine but still easy to cut with hand tools. In my experience, I find that it tends to be straighter and less warped than pine, although it costs more. It looks very nice with a couple of coats of Varethane.
Note that the end of the layout needs to be extended down to interface with the traverser (pictured below).
The ball bearing drawer sliders I use on Fillmore are from Home Depot. I would recommend getting them first and then finalizing the design. It might be possible to get away with only one drawer slider for this design. However, I propose two for more stability as the staging traverser is quite long and attached at only one end.
The drawer sliding arm can be separated from its assembly. This is needed to mount them with screws (usually supplied) to the wood. Because the 1×3 Upright (pictured below) is somewhat narrow, small mounting holes for those screws will likely need to be drilled into the slider arms. This should pose no problems.
Positioning the traverser: I would position the sliders in the retracted position against the layout. Then I would pull the arms out a little (~1/2”) to make some clearance (the traverser, when fully back, will over-travel the rear layout track by ~1/2”). The traverser would be aligned to the layout track farthest back. With enough stroke, the sliders should bring the traverser to the track nearest to the front of the layout. In the picture below, the traverser is positioned in the middle of the layout – note that the two slider arms attached to it protrude out as it is slid to the front of the layout.
This isn’t a difficult thing to build for someone who has built benchwork, but a good challenge. Temporary shims can be used to get the needed clearances versus the layout end while the parts are being assembled.
However, super-accuracy is not needed. There is a means to adjust for the rail height using permanent shims – one set at each end of the traverser. These can be made-up from styrene sheet and tacked onto the shimming ledge.
Mounting of the traverser to the layout is by two 5/16-18UNC or M8x1.25 bolts and wing nuts (the wing nuts go inside the layout end). I would also use washers to distribute the tightening load onto the relatively soft wood. A “C” clamp could be applied temporarily to hold the traverser in place while the bolts and nuts are installed (the clamp is removed before tightening the nuts).
The safety shields to keep that locomotive and cars on the traverser and off the floor, can be made with hardboard or Plexiglas.
The ball bearing drawer sliders on Fillmore that traverse have enough friction to hold their position for operating. Therefore additional alignment and locking features are not needed. I expect the same for this design.
The pictures below show the general arrangement with annotations.