Preheat the oven to 350F. Line a muffin pan with parchment paper liners.
In a medium mixing bowl, whisk together the ground flaxseed and water. Let stand for 5 minutes to thicken. Then, whisk in the remaining wet ingredients (i.e., apple sauce, apple, coconut sugar, coconut oil, maple syrup, and vanilla).
In a large mixing bowl, whisk together the dry ingredients (i.e., spelt flour, almonds, cinnamon, baking soda, baking powder, sea salt).
Add the wet mixture to the dry mixture and use a large wooden spoon to stir until just combined (read: no flour patches remain). Be careful not to overmix—spelt has a delicate gluten structure, so overmixing will result in dry, crumbly muffins. The batter should be quite thick and fluffy.
Divide the batter equally amongst the 12 muffin liners. (Since the batter is quite thick and fluffy, an ice cream scoop is great for this job, but you can also go the double-spoon, scoop-and-slide route.)
Garnish the top of each muffin with a light sprinkling of slivered almonds. Press down lightly to ensure they stick to the batter.
Bake for 16 to 20 minutes, or until a toothpick inserted into the center of a muffin comes out mostly clean with a few moist crumbs at the tip.
Cool in the pan for 5 minutes or so, and then transfer to a wire cooling rack to cool completely.
Wrap the muffins and store them at room temperature for up to 5 days or freeze for up to 1 month.