Generally we'd only create new cards when we run into a verb form in the wild (as it appears in whatever example sentence we run into). If we're having trouble with a particular conjugation, then we'll get example sentences for every conjugation form of a particular verb (different sentences for each form), and put those into my flashcards, but once you've done that, then you usually won't need to do that again for verbs that follow that particular pattern. So if conjugating Schlafen is difficult, you might use a bunch of sentences for that verb, but afterwards, you wouldn't do the same thing for, say, Braten.
You may prefer what we've been doing lately with Spanish:
Here's "hice" (I did), the past tense first person form of "hacer" (to do):
(answer "Hice. Root/Base Form: hacer")
Just says "hice". Back side has example sentence.
Says "hacer". Back side has example sentence for "hice" and says that "hacer" is the root/base form of "hice".
If you're plateauing, try playing around with this: https://fluent-forever.com/hacking-fluent-forever/ - do one or two hours of that, try to focus on talking about stuff that's difficult to talk about, and see whether you develop a lot of content that works specifically around your weak spots.