While I don't write as often as I would like, I find the corrections invaluable. I carry around an actual notebook and copy some of the corrected sentences to the notebook as part of my daily "Gold list" exercise. You can look up "Gold List method" on Youtube for more explanation in case you're not familiar with it. I'd prefer it over flashcards.
How interesting to hear! I do exactly the same thing after discovering the Goldlist method about two and a half years ago. I also use this method for lesson corrections as well as for new vocabulary from my reading and listening. Currently goldlisting in four languages.
I have never tried to create flashcard out of my notebook corrections, but I think it's a good idea. I think we can on one side, write the sentence in our native language and on the other write, the sentence with the correction in the target language, or on one side, just leave a blank on the correction (if it´s a word or a group of words) and on the other, write the whole correction. Any other ideas?