When I designed the Atlas pattern I had to sew approximately 500 billion curved pieces to test the pattern, so I reached out to a sewing forum to see what the preferred method was. Answers ranged from, "don't sew curves" to pins and glue, to slow and steady.
Since that time, I've become obsessed with the 1/4" guide method of sewing curves. This method uses a foot with a vertical 1/4" guide that sometimes comes standard with your machine. You can find an example here or here
To begin you will want to fold your curved pieces in half and mark the halfway point with an erasable pen, or chalk pencil.
1 place the larger, outside curve on the bottom, with the curve going to the right. The smaller pie piece should be placed on top the curve going to the left.
2 Your Right hand will guide the piece on the bottom and your left hand will guide the piece on the top. Guide them as you sew so that their respective edges align with the foots guide.
3 Every so often, check to make sure that the center markings of each piece are lined up, and smooth out your fabric if it becomes bunched.
4 Use bent tip tweezers to finish guiding the last little bit of the curve through the machine.
Because writing about this method is far more complicated than showing you, I put the directions in a short video to help you understand the method. Sewing this way can cut your time down to only seconds per curved piece, and will make your life much easier. It may take 2-3 practice runs to get it down, but anyone can master this technique.