Preheat the oven to 160 degrees and start up your grill (broiler).
Grind the flaxseeds in a spice grinder, then mix with the water in a small bowl. Set aside.
Remove the skins from the hazelnuts: on a baking tray, toast the hazelnuts under the grill until they begin to smell lovely and their papery skins turn a little darker. Roll the nuts in a clean tea-towel until most of their skins have come off. Don't get too hung up on removing every little bit though.
Grind the hazelnuts to a powder in the spice grinder and add to a large mixing bowl. Add the rest of your dry ingredients and mix together with your hands. (You can attempt with a spoon if you're squeamish but it's much easier with your hands)
Shape into ping-pong ball sized pieces and press down on a baking tray to cookie shapes. I wasn't sure if they would spread out, so I placed them very far apart but they could go closer than in the picture.
Bake at 160 degrees for 15-20 minutes.
Recipe by Veggie Runners at https://www.veggierunners.com/2014/04/21/vegan-nutella-cookies/