Fill directly mesial root and isthmus or distal root with your preferred material. If you want to try the cut of the apex work on palatal root and fill it!

Place your repair material inside a small hole, positioned by side inside pulp chamber

Place fibrine first and repair material after inside a perforation positioned in the middle of the floor. Be sharp, the challenge is also to avoid placement of the material inside root canals

Try to perform a perfect direct apical plug, placing a fibrine support over the apex, under red mark and after the repair material. Three millimeters are enough, but remember that this apex has a diameter around 200.

This is a real challenging situation! 
Try the sandwich technique described by Styleitaliano Endodontics and place your repair material after a short gutta-percha cone. Take your time, is the most difficult tooth

Style Italiano Endodontics Gold Member