Arrange the racks in your oven to accommodate the meatballs on a higher rack and the spaghetti squash on a lower rack. Preheat oven to 400° F. Line a large sheet pan with parchment paper.
Cut the spaghetti squash in half the long way as evenly as possible. Place cut side down on a medium sheet pan (no parchment paper necessary).
Make the meatballs: in a medium bowl, combine all of the meatball ingredients and mix with your hands. Roll into 1 inch round balls. Place in a single layer on the parchment paper lined sheet pan. You should have 30-35 meatballs.
Put the meatballs on the higher rack and the squash on the lower rack. Bake the meatballs for 23 minutes. Remove meatballs from oven and move the squash to the higher rack. Keep the squash in the oven for another 10-15 minutes until the skin is tender. When the skin is pressed it will leave an indent.
While the squash finishes baking, heat 1 tbsp olive oil in a large sauce pan (I used a 6 quart) over medium heat. Add the minced garlic and saute until fragrant, 1-2 minutes. Add in the marinara sauce and meatballs and stir. Keep at a low simmer until the squash finishes baking.
When the squash is done cooking, remove the seeds and slimy middle part with a fork and discard. Remove the threads with the fork and add the threads to the sauce pan and stir. When combined, add the mixture evenly to the squash halves.
Optional step: return to oven for an additional 5-10 minutes until warmed through. This step is really only necessary if you are adding cheese to your squash boats. Remove from the oven when the cheese has melted to your liking. Garnish with fresh basil leaves and enjoy!
