Ok so this may be a total dum dum question... but how exactly do you go about omiting a zipper? I hate zippers!
Do you have a specialpattern in mind? Using a fabric with more stretch is one possibility. Cuting the pattern pieces on the bias also ads a bit of strech but you need more fabric.
Mena (and some others, including me) do this when making a dress. You just sew up the centre back seam, or side seam, as it may be. If you can get the dress over your head - you have "passed the Mena test".
Being a pear shaped woman (small bust and waist, large hips) I have decided I can no longer make dresses like this - because I need them to be more fitted at the waist - and then they can't fit over my shoulders.
The sound of stitches popping - not what you want to hear!
I prefer to use a zipper unless the dress is very loose or stretchy. I have one dress I made years ago - for my wedding actually. I still have it as a special occasion dress - it's not white and lacy! It has no zip, but is so hard to get on I need help then am very hot and bothered by the time it's finally on. I can recommend some easy ways to put zips in if you like.
I used to hate zippers, too! Ironing invisible ones, sewing close to the edge. Serious loathing. Then I learned how to do a lapped zipper, and it has become a breeze to install them! I hope this helps you out in some way :)