Flexi defaults to Bootstrap-style class names, so you should be able to drop in HTML with Bootstrap class names and have it "just work".
Alternative class name styles can be achieved by altering your
config/flexi.js. See Foundation for an example.
If you want to rely fully on the Bootstrap CSS, you can also tell flexi not to include any of its CSS in
Note that if you do this, you will have to include Bootstrap CSS yourself, and that flexi elements and attributes will no longer be styled.
Updated less than a minute ago