Although it is possible to quickly hem without a sewing machine by using any number of heat fusible type products, the tried and true methods to finish a garment hem is by hand or by machine or a combination of both.
Unless a hem is to be topstitched and decoratively embellished by sewing machine or serger, it should be as invisible as possible. Before marking the hem edge on a dress, skirt or even a pair of slacks, it is best to hang the garment on a hanger for at least one day to allow the grain line to hang true. This is important for knit garments and those cut on a bias, like a full flowy type circular skirt.
Measure and mark the desired hemline with pins or with chalk (dark fabrics) or your favorite fabric marking tool (lighter fabrics) that can be removed with a damp cloth, or steam heat from an iron or by washing.
Most hemlines on skirts or dresses are 1 and 1/2 to 2 inches. Trim away any excess hem allowance over that amount and finish the raw edge either using a serger or zig zag stitch. If the fabric is bulky, trim seam allowances under the hem to 1/4 inch to reduce bulk at the seam lines.
Turn up the hem along the prior marked edge, but be sure to match seam lines first, then pin in place. Try on the garment again to be sure the hemline is exactly where desired.
Some sewing patterns will suggest to turn up the hem allowance, then turn under the raw edge 1/4 inch, press and stitch near the edge. Stitching will of course be visible on the outside of the garment. This is a quick method for creating a hem on casual clothing. For more professional clothing an invisible hand titched hem is appropriate.
To minimize the look of hem stitches when hemming by hand, be sure to catch only one or two threads of the garment and more of the fabric within the hem allowance for support. A double thread through the hand needle is not needed as a single thread will be more than enough to keep the hem in place. A few extra stitches at the seam line intersections can ensure additional support for the hem.
A machine zig zag finish for a hem allowance edge, stitched close to the raw edge of the hem, is sufficient for knits if the edge is not serged. Hem by hand using small criss-crossing catch stitches or slip stitches from the garment to the hem edge.
For the adventurous, a hand rolled hem can be used with sheer or lightest weight knits. Trim the hem edge to 1/2 inch, turn under1/4 inch, and roll the hem under yet another ¼ inch. Using the smallest of stiches catch a thread or two of the garment edge and a stitch of the rolled edge. There are specialty presser feet that can do this rolled edge hem in a short amount of time as well.
There are many, so many other ways to finish a garment edge – using bias binding, serging, machine or hand blind-stitching (hides stitches in the folds), adding lace edging to the raw edge then hand or machine stitching, pinking the raw edge, then fold and stitch or fold to add fusible hem tape and press to fuse, even twin-needle stitching on knits (single fold hem) are just a few other ways to accomplish this necessary task.
There are no real sewing rules for hemming. The functional use of the garment, fabric types and personal preference usually determine the type of hem to apply.
Sew happy, sew inspired.