Two flows on one page problem (basic question)

I have a Prelude and Sarabande to lay out. As the Prelude finishes halfway down page 3 I made a new Master page (based on default) with another frame below for the Sarabande for both pages.
Unfortunately I either get the Prelude starting again at the bottom of page 3 or the Sarabande as it should, but not flowing to page 4 (page 4 just starts with the Sarabande again).
I found that changing the master pages needs an update to the page by removing the master page settings before applying the correct (again) master page. I presume this is what you need to do each time?

(I only have one instrument being played)

If someone could tell me how to do this I would appreciate it.

While you can, you don’t have to fiddle with master pages for this, as you may need to adjust the frame chains… You can instead allow flows to start on existing pages (Layout Options/Page Setup/Flows/Allow on existing page.) Then your Sarabande will start after the Prelude, and continue on page 4 automatically.

Thank you this worked.
I will go back to what I was trying to do another time so I can figure it out in case I will need to do it one day.