there is not much to laying flex track on cork roadbed.
mark centerline with pen/marker. tie a string to it to make large radius's . mark any easements that you doing with more radius. spread adhesive caulk (ie dap...) lay down cork in halfs along the centerline, it will grab fast, yet will be somewhat adjustable. put weights (cork is springy in curves), let it dry for couple hours and repeat with other half. the joint will mark the centerline and tacking down flex sections is no brainer. before putting rail it is a good time to paint your roadbed grey if you so want.
it is arguable where the sliding rail goes, some do on the inside , some on the outside. it is not possible to curve the very end of the flex so plan on last inch or 2 being streight. when joining flex to to ordinary section i stager the joins, meaning make the rails different length (easi since one for the rails) , cutting the rail but not the plastic tie grid. then the i slide the extra length into the plastic. i solder and polish all my joins.
flex rail on the left, rigid section on the right. line marks where the tie grid of rigid section ends (since then i resoldered the joins for cleaner performance) so the flex conforms to section shape exactly and transition is seamless.