Today I cut out the paper template, glued the major portion down to a 2×8 sheet of Homasote I made earlier and jigsawed it out. Usually one glues the Homasote to plywood subroadbed and then cuts them both out together but I wanted to mitigate issues at the baseboard joints. Homasote is not perfectly even whereas plywood usually is so I will but plywood at the join but span the joint with the same Homasote sheet and cut it afterwords.
If you have never used Homasote, it is a compressed paper product originally intended for sound proofing in building construction however it is popular enough among model railroaders that model railroading gets a mention on their website. The downside of cutting Homasote with any kinds of power saw is that you get dust. Lots of it. My shop floor paint is not peeling, that is drifts of sawdust. Ideally, you do the sawing outside but that was not an attractive option in Toronto in January. The job is done but I intend to experiment with cutting it with a utility knife for the remaining tail tracks.