Fields and Flags plays very much like minesweeper. The difference is that you start with a bunch of money and if you make a mistake it just costs you money, rather than ending the game.
Another difference is that you don't get long to decide which squares are potentially mines or not. After a short time the grid will start revealing itself anyway, so you need to stay one-step ahead. Which is definitely easier on the smaller levels, and much harder on the bigger ones!