A notebook you sewed yourself opens differently.
Short notes on binding small books at a kitchen table, with a needle, linen thread and a few sheets of good paper.
Find the grain first
Paper bends more easily one way than the other. Fold along the grain and the pages lie flat; fold against it and they fight the spine for years.
Fold in small groups
Four or five sheets folded together make a signature. Thin signatures turn smoothly and keep the fore-edge from creeping outward.
Pierce before you sew
Mark the stations with a simple paper jig and pierce every signature at once. Even holes matter more than a fancy stitch.
Let the cover come last
A plain board wrapped in cloth or heavy paper is enough. Press the finished book overnight under a stack of heavier ones.