Flash Fiction Magazine offers a Flash Fiction Masters feature where for $25/month you can get personal feedback on a new flash story every month (or $20/month, if you pay for a year in advance). Plus, you can be part of a closed Facebook group where members share drafts and get detailed feedback to hone their craft before submitting. https://learn.flashfictionmagazine.com/p/flash-fiction-masters

For those who don't want that level of commitment, Flash Fiction Magazine also offers Priority Submissions where for $30/story you can get in-depth feedback on your story from their editors. #Feedback