Fold a double-layer piece of aluminum foil into a 12 by 9-inch sling. Set aside.
In a medium bowl, whisk together eggs and chicken broth. Add breadcrumbs, whisk to combine, and allow to absorb all of the moisture.
In a microwave-safe bowl, combine olive oil, onion, celery, and garlic. Heat on high power until tender, about 4 minutes, stirring halfway through. Add more time, if needed, in 30-second intervals. Alternatively, saute vegetables in a medium skillet over high heat, about 6 to 8 minutes. Cool the mixture in the refrigerator for 5 minutes.
In a large bowl, add the ground beef, Parmesan cheese, breadcrumb mixture, cooled vegetables, tomato paste, parsley, soy sauce, Worcestershire sauce, paprika, salt, pepper, and thyme.
Use your hands to gently mix the ingredients until combined, about 1 minute, being careful not to overmix.
Shape the meat into a 9 by 4-inch domed loaf, about 2-inches tall. Place it in the center of the foil sling. Then grab the edges and carefully transfer it to a 6-quart slow cooker.
To make the glaze: In a small bowl, whisk together maple syrup, ¼ cup tomato paste, apple cider vinegar, ½ teaspoon Worcestershire sauce, ½ teaspoon salt, and ¼ teaspoon pepper.
Add 3 tablespoons of the glaze to a bowl. Brush over the top and sides of the meatloaf. Reserve the remaining sauce to use for topping later.
Cover and cook until the internal temperature reaches 155 to 160ºF (68 to 71ºC), 2 1/2 to 3 1/2 hours on low setting. It takes about 2 hours and 45 minutes in a crockpot.
Carefully remove the meatloaf using the sling, draining the juices into the pot. Transfer to a cutting board. Rest for at least 15 minutes before slicing.
Brush the top with the remaining glaze or serve on the side. Cut into even-sized pieces. If not serving immediately, transfer to a cleaned slow cooker, cover, and keep on the warm setting for up to 1 hour.
Breadcrumbs: You can use traditional breadcrumbs, but the texture will be slightly denser.
Storage: Cool completely and store in an airtight container in the refrigerator for up to 5 days. It’s easier to reheat sliced pieces.
Extra sauce: Double the glaze for more sauce to serve on the side.
Broil (optional): To caramelize the crust, broil the meatloaf on a foil-lined baking sheet. Set the oven rack 6-inches away from the broiler element. Heat the oven to broil on high. Brush the top and sides of the meatloaf with the remaining glaze. Broil until the surface lightly browns, about 5 to 7 minutes. Keep a close eye on the oven as it could burn!