Preheat oven to 375 degrees. Place berries, arrowroot, coconut sugar, and maple syrup, and vanilla into a large bowl and gently toss with a spatula until everything is distributed.
Place oats, pecans, maple syrup, and coconut sugar in another large bowl. Toss together until well combined. Add butter to mixture and fold the oat mixture around the butter. Continue to combine until the whole mixture is crumbly and holds some shape when pinched or scooped. Use hands if needed.
Grease a baking dish. Place berry mixture into dish. Top with oat mixture. Make sure oat mixture is evenly distributed across the top of the berries.
Bake in 375 degree oven for 30-40 minutes. Check at 25 minutes. If topping is dark brown, remove from oven. Allow to cool for about ten minutes before serving. Can be served with vanilla ice cream or topped with whipped cream.