Mother's Day Tennis Dress and Sewing "in the Flat"

Yesterday for Mother's Day, my sweetie pie husband gave me the day off. He cooked all of our meals and cleaned up too, and I was free to get some good sewing time in. I made a dress for the baby in a cute little retro print synthetic knit I found thrifting for a quarter.

For the second time now, I sewed an entire garment "in the flat." Does anyone else do this? What the heck do I mean? Well, the instructions for the pattern I used, Butterick 5976, would have you sew the side, back and shoulder seams, then attach the collar and facing, insert the zipper next, and then ease in the sleeves and hem them (those tiny little sleeves!) before hemming the dress bottom.

Here is what I did:

1. Serged the shoulder seams together and pressed them backward
2. Eased in the sleeve cap and serged into place
3. Serged sleeve hem and hemmed/stitched the opening of the sleeve while flat 
4. Sewed the collar as usual. Serged bottom of facing and attached facing and collar to dress
5. Understitched facing and instead of tacking stitched facing to shoulder it in the ditch through the top of the shoulder seam
6. Serged both sides of back seam separately then sewed to zipper bottom position. Inserted zipper, and hand slip-stitched facing edge at top of zipper
7. Serged side seams and sleeve seams all at once. Pressed seams toward back. Alternately (to allow for small adjustments later) you could serge front and back individually and sew
8. Serged hem and hemmed it

I don't know if there is any reason not to sew this way, but I have been finding many aspects of construction easier when garments are sewn in the flat- especially kids stuff. Um, and zippers! If you are machine sewing a zipper, it is way, way easier to sew it flat without all of that extra fabric in the way. And why fuss to fold and hem a tiny sleeve when you can just sew it flat? Yes, this does make a seam that ends at the armscye, but isn't that seam hidden by the child's arm anyway? 

I'd really be interested to know if anyone else sews this way or has tried it, or if anyone knows of reasons why it might be a bad idea. 

Now that I've rambled on, here are some pics of my little munchkin in her new dress.

Courtesy of the Vintage Pattern Wiki

It is great how she is so excited to wear a dress I have made her. Sometimes she comes to me with a shirt or scarf and says, "Mommy, I made this for you!" It won't be long before we'll have a little sweatshop going!