Cookie Cutting Method

I’m working on a layout using Kato unitrack N gauge. I have my track all layed out, but before I begin cutting I would like to know if I should cut exactly along the traced edge or leave a little room on each side of the track for ballast. Or with Kato track do you need to add ballest because of the way the unitrack is made. If I do need to leave space on both sides how much should I leave?
Thank you all in advance for your help and information.

Louie

Louie, I am also using only Kato track and plan to use it on homasote and do some cookie cutting. I would leave some room, maybe at least 1/8 inch , on either side of the track to attach scenery, trees, signals, etc. I do not plan to use ballast since it can mess up the working of switches and the Kato track does not need it. I do not plan to use white glue and water since the water base will mess up the homasote.