I am not a big fan of ironing. In fact I will tumble clothes in the dryer over and over again to avoid ironing and one of my very favorite new products is Downy Wrinkle Releaser. Having made that perfectly clear, I would now like to state that there are sometimes when you just have to iron, and pressing seams is one of them.
Hand-sewn seams are most often not pressed open, because the seam will be stronger if the seam allowances are pressed together to one side.
Unless directed differently in your pattern instructions, machine-sewn seams should first be pressed to one side, just like hand-sewn seams, and then opened and pressed flat. This is probably an extra step that you aren’t used to taking, but trust me it will be worth your while to press your seams in this manner.
If you don’t already have one, you might consider getting a tiny quilting iron to use when pressing your doll clothes seams. They should be available at quilt and fabric stores in your local area, and they are certainly readily available online. This is a link to Connecting Threads, one of my favorite online sources for quilting supplies.
For all of you non-ironing fans, like me, cheer up. There is absolutely no reason at all for you to press seams when you are sewing your doll. You just need to iron her clothes.