I do two methods depending on items at hand. ( I didn’t click the links below so if I’m repeating a method please forgive me!)
You can crack an egg into a coffee mug, mix up, cover in a wet paper towel and microwave for 1min/70sec. It might make a pop sound but that’s all fine. Comes out pretty sandwich appropriate.
Easy to make morning of or make at work or whatever.
I use a silicon muffin tray. Spray/apply oil to cups and crack one egg into each for however many you want. If you don’t mix the eggs together, just pierce the yolk with a fork. I sprinkle black pepper on the top of mine. No need for cup liners.
I’ve mixed in bacon bits, basil leaves and really whatever else. 350°F / 177°C for 15-20 mins, adjusted to your preferences.
I imagine those would freeze up very well. Now, I’m going to go make a breakfast sandwich for dinner! Good luck!