In the past, I had a plywood base with roadbed, so under the table switch machines were easy enough to mount. I built my new layout on a door base with 1 inch foam base and the linkages are not workingwell with the long distance between teh switch and switch macine. Can I mount the switch machine directly under the switch and just dig out underneath it to make room for the switch machine?
Yes, clearly you can if you want to do all that work. You can also try mounting the switch machines on the surface and use a brass rod to connect to the linkage. This way you could even mount the switch machines at the edge of the layout and bring the movement into the switch with a brass rod.
Here are some that I have mounted on my layout. Since this section is built on a little table sitting on a bigger table, I cannot access the underside to mount motors, in this case Tortoises. I routed out a path to the edge of the table where I will mount the machines, connect them with a 1/16" inch welding rod (A 1# pack is less than $5.00 and will give you over 100 feet of material) Scenery can be built right on top of it, and switch machines can be disguised in buildings. I’ll not bother here since that area of the table is “off stage”.
ROAR