Heat a large heavy bottomed pot over medium-high heat and add bacon. Cook, stirring occasionally until crisp, about 6-8 minutes.

Lower heat to medium-low and add sliced onion. Cook until beginning to soften, 7 minutes, stirring to prevent burning.

Return heat to medium heat and add 1/4 of the collard greens and 1 cup chicken stock. Scrape up any browned bits on the bottom of the pan and let the greens cook down a bit until you can fit more in the pan. Continue to add more greens until all are able to fit in the pan.

Cook, stirring occasionally until the greens are completely wilted down and have changed color to a dark green, about 25 minutes. Add more liquid if it has evaporated before the collards have cooked down.

Add coconut sugar and apple cider vinegar and and continue to cook until most of the liquid has evaporated from the pan, about 5 more minutes. Taste and season with red pepper flakes, and salt if needed (though do taste, as the bacon will add quite a salty flavory). Serve immediately.