Warm the coconut oil in a medium saucepan. Don't boil it. If it's cold in your house make sure it gets fairly warm because it will solidify very quickly.
I ground the cacao and Xylitol until fine powder. The cacao was a powder but it had lumps, the Xylitol is very gritty. The bark tastes better if you grind these two ingredients really fine. Carefully add all of the ingredients into the warm coconut oil. Stir well to combine. Keep warm.
Cut a piece of parchment paper to fit in the bottom of a 8x11 1/2 inch cookie sheet with 1" sides. Pour the warmed mixture onto the parchment paper. The bark will be about 1/4" thick, the smaller the pan, the thicker the bark.
Put the pan in the freezer until it sets. Making sure the pan is kept even, otherwise the bark will be bigger at one end then the other. Thirty minutes should be plenty. I found my bark set up before that, but it doesn't hurt to leave it for the full time.
When it's set, remove the tray from the freezer and lift it out of the pan and break it up into pieces. Store in the fridge, otherwise it will melt very easily.