I have not done coroplast, but I have done a bunch of signs (Metal) and mirrors. I would (I think) approach coroplast the same way.
I use a large cardboard type of cutting mat, similar to this: http://www.uscutter.com/Self-Healing-Cutting-Mat
I use this just to lay my project on and center things up with the grid. When I do my stencil, I place registration marks at the outside centers.
When I apply the application tape, I make it long on one end that I make the "top end". Then I use parchment paper and hinge it like 'goose has shown in the past.
This allows me to lay the vinyl down on the project, center it up with the grids and when I have it placed I then secure it with the long end of application tape. The rest is as shown in 'goose's video. Works good for me.
Now, for coroplast I might investigate getting a piece of plexiglass the same or close to the same thickness. Just a piece 3-4" wide and a couple inches wider than the coroplast. I would tape this to the cutting mata so that the coro was centered where needed and use this both as a "stop" for the coro and as a leveling tool to fasten the application tape to.
I hope this all makes sense.