Preheat your oven to 350°F (175°C). Lightly grease an 8x8-inch baking dish or similar.
In a large bowl, combine the sliced peaches, lemon juice, vanilla extract, ground cinnamon, and cornstarch (if using). Add honey or a sugar substitute if the peaches need extra sweetness. Toss everything together until the peaches are well-coated. Pour the peach mixture into the prepared baking dish.
3 peach, 1 tbsp lemon juice, ½ tsp vanilla extract, ½ tsp cinnamon, 1 tbsp corn starch, ½ tbsp honey
In a separate bowl, mix together the rolled oats, almond flour, flax seed, chopped nuts, melted coconut oil or butter, brown sugar, ground cinnamon, ground nutmeg, and a pinch of salt. Stir until the mixture is well-combined and crumbly.
½ cup oats, 2 tbsp almond flour, 3 tbsp flaxseed, ¼ cup nuts, 2 tbsp coconut oil, 1 tbsp brown sugar, ½ tsp cinnamon, ¼ tsp nutmeg, 1 pinch salt
Evenly sprinkle the oat topping over the peach filling in the baking dish.
Place the dish in the preheated oven and bake for 30-35 minutes, or until the topping is golden brown and the peach filling is bubbly.
Allow the peach crisp to cool for a few minutes before serving. This helps the filling set a bit. Serve warm, optionally with a dollop of Greek yogurt.