How to associate layout with projects
As probably you have read before, you can decide which project fields you want to display per project/space in the Layouts. The layouts are like the project schemes in Jira.
Associate a layout to one or more projects and spaces
From the layout manager click on Associate
After click on "Associate projects" you just need to select all the projects you want to have that layout, and save.
Switch layout in one project
You can change the layout in the project tab. If you switch to another layout you don't lose the values of the fields.
After click in "Switch layout" you can choose from the different layouts created.