You don't need turnplates, they simply allow you to take the wheels with the steering unlocked and turn them in and out 15* without getting up and reaching into the car or walking around it.
I'm starting to think the use of turning plates might actually be necessary depending on the surface the tire is sitting on and the size of the tire.
Years ago I aligned my Duster using these methods - front bolt out, rear bolt in, adjust the rear bolt to get a reasonable camber, then a tape measure to adjust toe. Car drove great for years, never did see an alignment shop. This was with a 14" ralley wheel and tire in the dirt.
But recently I have been chasing my tail on this thing. I have 17x8 wheels with 245/45R17's on it and am now in a shop with a concrete floor. I think my issue is that things are just too stiff to accurately see the change when I adjust my toe. Pretty sure some turning plates to reduce the resistance are the key (for me).
I had planned to pick up some mason boards and put some grease or something between them. But I like the idea of trying some wax paper first.