Make the compote. Combine blueberries, maple syrup, lemon juice, and cinnamon in a small saucepan over medium heat. Simmer 5 minutes, stirring occasionally, until berries break down.
Thicken. Stir in the cornstarch slurry and simmer 2–3 minutes more, until thick and jammy. Remove from heat and cool to room temperature.
Mix the oat base. In a jar, combine oats, plant milk, yogurt, chia seeds, vanilla, and cinnamon. Stir well.
Layer. Spoon cooled compote into the bottom of the jar, then top with the oat mixture. Cover and refrigerate at least 4 hours, or overnight.
Top and serve. Stir or leave layered. Top with peanut butter, granola, and extra blueberries just before eating.