My book, Flash Fiction: Alive in the Flicker, A Portable Workshop is available at https://tinyurl.com/42snuxn7 It includes a history of flash fiction, explorations of different types of flash fiction, markets, a marketing strategy, and lots of exercises and prompts.
My articles and essays on flash fiction have appeared in many publications: Writer's Digest (and their other publications), Rose Metal Press's Field Guide to Writing Flash Fiction, and in Critical Insights: Flash Fiction (and others). For years I taught online courses in flash fiction and haibun. I also ran a popular online critique group for flash fiction that began in 1998 and stayed active and popular for over 15 years. I'm now the Senior Associate Editor for OPEN: Journal of Arts & Letters.