Thick notebook question.

Well, you could argue that it's me that is thick (and be on pretty solid ground), but anyway...

If you have a thick notebook that opens on the long spine, do you place something underneath the side you are writing on to bring it level with the thicker side (if you see what I mean)? If so, what do you use?

I use another book. My library has many different thicknesses.

I typically slide my phone beneath the thin side. I always have my phone so it becomes an easy habit to develop.