To square up the top, I had to plane end grain.
I have a block plane, but it's really bad so I decided to use my Groz #4. The main problem with a piece this large is holding it. What I did was clamp it low in the side of the vise and rested the bottom on a sawhorse. Don't forget to clamp a block on the back to prevent tearout. Clamping the block with its end grain on the piece's long grain makes this slightly more pleasant.
The result? A smooth flat surface and killer details.