How to allow user to select MFA method during signing in to AD B2C Auth App Or SMS?

Question

We would like to allow users to select MFA method during signing in.

1. User goes to our App
2. App redirects the user to the AD B2C login page
3. user authenticates using e-mail + password
4. user selects MFA method (phone or e-mail)
5. user types the verification code that they got from Step 4
6. user is redirected to out app

So how would one go about doing this? Do note, we are using custom journeys.