Flash Fiction Online is a pro-market for flash pieces:
Every month, Flash Fiction Online is proud to publish what we think is some of the best darn flash fiction there is. Each issue includes three original stories by both new and seasoned authors. Although many on our staff have a fondness for the speculative, we enjoy and select fiction in any genre. Founded by Jake Freivald in 2007, Flash Fiction Online has been published by Anna Yeatts since September 2013.
They're paying $60USD for unpublished flash, and 2c/word for reprints. Certainly worth your time, flash fiction writers. They'll also accept up to 3 pieces at a time.
Check the listing here: https://literarium.net/market/flash-fiction-online/flash-fiction-online/