There are different ways to construct a double wedding ring. Some people simply applique down the rings on to a solid backing. I know a lot of us fear/don't like working with curves but for the most part these are large and gentle arcs, not tiny little drunkard's path patches.
I'd say to try it out first with a few scraps before fully committing to the project. I would recommend getting a template set and reading and understanding the directions. Some have only one wedding ring piece shape, with some kits that is correct and precise, with others you trim a bit after you attach so read your directions. Other kits have L/R end pieces with all the same in the middle.