Preheat the oven to 180 C/350 F. Grease a 9 x 13-inch dish and set aside.: The oven should feel warm as you step away, and the initial scent of heat primes the baking environment. Preheating ensures the dish begins cooking immediately, producing even bubbling in the filling later on. If the oven is not fully heated you may see the top brown unevenly and the filling may take longer to thicken, so wait until a thermometer or the oven indicator confirms the temperature. A common mistake is not greasing the dish well, which can cause sticking, so take a moment to coat it evenly with oil or nonstick spray and tap out any excess.
In a mixing bowl, combine all your filling ingredients and mix until combined. Transfer to the greased dish and spread out in an even layer. Place it in the oven and par-bake it for 15 minutes.: At this point you will notice the fragrance of fresh peaches and lemon juice , bright and fruity, as they mingle with the sweetener. Par baking helps the fruit release juices and begin to thicken, avoiding a soggy topping later. Use a spoon to spread the filling evenly so every bite cooks uniformly, watching for gentle bubbling at the edges as a sign it is ready. One trap is skipping the par bake, which can leave the topping underdone or the interior overly watery, so trust the time and the visual cue of gentle bubbling.
While the peach filling is baking, prepare the biscuit topping. In a mixing bowl, whisk together the almond flour, arrowroot powder, baking soda, and salt. Add the coconut oil, maple syrup, and milk, and whisk together until a thick dough remains.: You will feel the dry ingredients lighten as you whisk, and the aroma of almond flour and maple syrup becomes noticeable when the wet elements hit the bowl. The dough should be thick enough to hold its shape when spooned, slightly sticky but not runny, and will have a sweet, nutty scent. This mixture needs only gentle handling because overmixing can make the topping dense; stop when the ingredients are just combined. A frequent error is adding too much liquid; if the batter looks soupy, add a touch more almond flour to bring it back.
Remove the baking dish from the oven. Drop spoonfuls of the biscuit topping onto the peaches. Place back in the oven and bake for a further 15-20 minutes, or until golden brown on top.: When you open the oven you'll be met with a rich aroma of warming fruit. Nestle dollops of topping across the filling so there are small gaps where the filling can bubble through, creating a rustic look. The oven will start to produce toasty notes as the topping browns; aim for an even golden surface with slightly darker edges. Avoid overcrowding the topping, since larger clumps may not cook through in the center. If after 20 minutes the topping is pale, you can give it a couple more minutes, watching carefully to prevent burning.
Remove the peach cobbler from the oven and let it sit for five minutes before serving.: The resting period allows the filling to settle and thicken slightly, making it easier to scoop and enhancing the flavor as the juices cool just enough. You will notice the steam soften and the aroma mellow into a concentrated peach scent. Resist the urge to dig in immediately, as serving too hot can be messy and the texture will be looser. A common mistake is skipping this short rest and ending up with a runny serving, so give it those few minutes to set.
