So, you have a few signatures put together and you're ready to assemble your journal. I suggest you take a few easy steps first, to make your finished journal even more cohesive.
Step 1 - Page Placement
Take a moment to flip through your signatures and make sure the spreads that have been created look good. Some papers might not look good next to each other. Rearrange them if need be.
They certainly don't have to be perfect. A lot can be done to bring two pages together. But if you start with a good flow, it's all easier from the start.
Step 2 - Sewing
If you want to add any sewn pockets or other sewn elements directly to your journal pages, now is the time. It's SO much easier to sew onto a single page than it is to sew into a completed journal.
This pocket was sewn onto the page before the signature was sewn into the journal.
Step 3 - Weird Experiments
If you have any weird ideas you want to try, It's best to try them on a single sheet of paper before your journal is assembled.
I tried spackle paste on a stencil here. I was afraid it would wrinkle the page and also that it would flake off when dry. Neither of these things happened, so I included the page in my finished journal. Had it turned out poorly, I would have just tossed it and added a different page to my signature.
Step 4 - Think About Tabs
Will your journal have tabs? If so, do you want the the journal cover to cover the tabs, or do you want the tabs to stick out beyond the cover? You might have to trim the width of your pages for everything to fit, and that's easiest to do prior to assembling the journal.
Step 5 - Make Connections Between the Pages
Lastly, do a quick flip through your signatures to see if you can add any cohesiveness to any of the spreads. Of course, you can do this after the journal is assembled, as well. But now, before any of the decorating, it's easy to add some elements to give your journal a good flow.
This pink and green page was next to a plain brown page. I added a pink and green belly band to give more flow to the spread.
This plain floral page was next to a page with a teacup on the bottom. I added pockets with a teacup to the floral page to echo the teacup on the other page.
This ledger paper was next to a page with pink florals. I added a pink floral pocket to the ledger page. Then I added a pink belly band to the floral page.
Once you've completed these five steps, you can assemble your journal knowing it will have very good bones. Here's a video if you are interested. Journal Making - Part 1 Have fun!