@Izzy Did and upvoted too, before your comment here. :)
@Izzy Is there a reason flashing boot partition would result in recovery installation? In this question android.stackexchange.com/q/120581/96277 OP flashed boot partition thinking that TWRP would get installed. I can't really get the point.
Bad luck if not even fastboot works. Only solution I could think of would be a bootable SD card – that was how I once recovered a borked tablet (failed update: it wiped everything first, and then figured the images were broken, yuck!)