Peel and chop the sweet potatoes into large chunks. Place the chunks in a large saucepan and cover with cold water, bring to a boil and reduce to simmer. Simmer until the sweet potatoes are fork tender, about 15-20 minutes. Once done, drain well and let cool.
Meanwhile, preheat your oven to 350°F and spray a little cooking spray on a 9x13 or 9x9 inch casserole dish.
In a mixing bowl, combine the pecans, oats, oat flour, and brown sugar. Cut in coconut oil with a fork or knife until the mixture is sandy with pea-sized chunks of oil. Set aside.
Place sweet potatoes into a large bowl and mash them with fork before adding coconut milk, maple syrup, oil, flaxseed, vanilla, cinnamon, nutmeg, and salt to the bowl. Mix until everything is combined.
Spoon the sweet potato mixture into the prepared dish and sprinkle on the brown sugar and pecan mixture.
Bake uncovered for 40-45 minutes, until the top is golden brown and the sweet potatoes are bubbling.