With this bookmark, which also serves as an excellent test for your first layer, you can determine which side to proceed to by observing the direction of the text.

The bookmark lies on the right page with the text readable.

There’s a nose/notch at the top so it holds better in your hand and fits better against the top edge of the book.

I’m printing it in:

0.4 nozzle diameter

0.2 layer height

1 outer wall

2 bottom layers and 3 top layers (concentric bottom layer for optimal appearance)

2 different colored PLAs