Dear Kevin,
I've never seen one of those full-page slates, but it makes sense. Sighted
people write line after line without pausing to change the paper every four
lines, so why should we?
As to the board slate, I like them because you don't need a solid surface to
write on. APH still sells them, but they're quite expensive.
I learned to use the slat when I was 11 years old at the California Braille
Jail and I was forced to stop using the board slate and use a pocket slate
instead.
Terri Amateur Radio call sign KF6CA.