What kind of track are you using?
My usual procedure is to secure an adequate subgrade (thin plywood) and a layer of extruded foam through the area where tracklaying is scheduled. Then I lay down sheets of cardstock (comes in 20" by 26" sheets) and locate such key items as curve centers (curves are marked by swinging a trammel - sort of like an oversize compass) and turnouts. The track plan is worked out with flex, and the tie lines are marked on the card stock. Not many rail joiners used at this stage, since the object is to get the card stock marked.
Once I've located all the track components, I cut out the templates, clear away the debris, re-lay the card stock (not the track) and determine where and what shapes of ballast former are needed. I use thin extruded foam, cut to appropriate shape and contour with a utility knife. (In the Dessicated Desert, cork is a non-starter. It dries up and crumbles, while the extruded foam is unaffected by high temperature and very low humidity.) The ballast formers are placed under the templates as they are carved, positioned with brads (toothpicks would probably do as well) then secured with latex caulk and weighted down with a choice collection of old phone books.
After the ballast formers are all in place, I caulk the cardstock templates to them and replace the phone books. The final step is to lay the track, which is finally trimmed to size, rail joiners installed, specialwork taken care of and everything secured to the cardstock templates with one final layer of latex caulk. The cardstock, which has been precisely marked, allows the flex to be positioned exactly: smooth curves, proper easements, no kinks. An hour or so under the phone books sees the caulk set up, and the track is ready for temporary electricals (alligator-clip test leads) and the designated derailment check train. Any problems found by the latter are fixed THEN, not set aside for later.
I usually lay a few meters of track at a time, then go back and proof check everything. I'm obsesso about getting it right - but once I do, derailments just don't happen.
Chuck (Modeling Central Japan in September, 1964)