As a FreeFlexer you can always get yourself substituted by someone else or act as a substitute for another FreeFlexer. One of the ways you can do this is through the Temper platform. How easy is that?
As a substitute you are required to independently complete the shift. Therefore you need to posses the skills required. If the shift, for instance, requires you to be able to walk with three plates, you must have this skill in your profile. Do you lack a required skill? In that case you can unfortunately not apply as a substitute.
Do you think you have the required skills but just didn't add them to your profile yet? Check here how you can easily add skills to your profile yourself.