I like to keep the eggs upright also when I candle, so just move your flashlight to the top and candle down.
Here’s a good candling article
https://www.backyardchickens.com/articles/development-of-a-chicken-embryo-day-by-day.72537/
Here’s a good candling article
https://www.backyardchickens.com/articles/development-of-a-chicken-embryo-day-by-day.72537/