I will try to explain how I sometimes press things when I only want to do one seam at a time -
When I pres this way, it is usually from the "right side""
I line up one seam about an inch (or whatever works with what you are making) from the edge of the ironing board - smooth the item as well as I can - and then i can press only up to that seam or more - it's a great way to get those pleats by the seams out because I can see them - and nudge them away with my iron.
Then I move the item so the next area is "in place" to get pressed/ironed/smoothed.
If I iron almost on the edge of the ironing board - it seems to work almost as well as those half dowel things for pressing seams.