Meatloaf: combine all meatloaf (not meatloaf glaze) ingredients in a large bowl. With your hands, mix the meatloaf until everything is well combined. 

Place all mixed meatloaf ingredients on a parchment-lined sheetpan and, using your hands, shape into a bread loaf-shaped mass. Pack it fairly tight so that everything stays together. 

Pre-heat oven to 425°F (220°C) and then add your meatloaf to the oven and reduce the heat in the oven to 350°F (177°C). 

Set a timer for 15 minutes and start to make your glaze. 

Add all meatloaf glaze ingredients into a small saucepan over medium heat. When brown sugar has melted and all ingredients are combined, take your glaze off the heat. 

Pull the meatloaf out after 15 minutes and, with a brush or spoon, paint the glaze on top every 15 minutes or until an hour has passed. After an hour, or 1 hour and 15 minutes, the meatloaf should be done, but you can check with a thermometer if you have one. The interior of the meatloaf should be at 155°F (68°C) when you pull it out. Carry over heat will bring the meatloaf to a safe 160 degrees. 

Sandwich assembly: remove the meatloaf from the refrigerator (or if the meatloaf is freshly cooked), slice a 3/4 to 1-inch thick slice. If the meatloaf is fresh from the fridge, you should warm it up. I prefer to do this in a medium skillet over medium heat. Warm the meatloaf for about 3 minutes per side until it's seared and warmed through. You can also heat it up in the microwave or in a 350°F oven on a sheet pan for about 8 minutes. 

If you're using cheese, add the cheese at the end of the warming process so that it can have a chance to melt just a bit. 

Toast two slices of bread and add mayonnaise and/or mustard or whatever condiments you prefer to the bottom slice. Then top it with the warmed meatloaf slice and top the meatloaf with several leaves of lettuce. 

Close the sandwich and serve.