Hi Brent 
Welcome to the community! 
Is there any particularly reason why you feel you can’t use out-of-box Auth0 sign up workflow? Instead of preferring to design and host the sign up workflow yourself.
Universal Login offers a whole range of customisation options as part of New Experience - the recommended experience; see here for more details. And also provides a Classic Experience which, being totally client-side rendered, can provide even more customization flexibility (see here for details) for more niche scenarios. Using out-of-box workflow also means you’ll benefit from a number of other features that are provided by the platform - like our Password Policy and also Breached Password Detection, as just a couple examples.