Bell Bottoms changed significantly from when they first began to be worn in the 60's until they finally
went away at the start of the 80's. They started out small as little flares just at the ankle or the
bottom of the leg, and kept moving up higher and growing wider and wider until you almost had the
equivalent of a full skirt just beginning either at the bottom or at the top of the knee in the middle 70's. Then, the entire leg of the pants began to flare until they became what were known as
"palazzo" pants (worn by women exclusively)
through about the mid 80s.
The Navy, by the way, just switched to stovepipe leg pants very recently, so the US Navy aren't
wearing bell bottoms any more.
You have 2 options. A flare leg or a true big bell bottom.
They aren't all that hard to make with just a simple insert. Just use a seam cutter to open
the outside seam of the pants leg from just below the knee to the hem and add a
triangular piece of matching or contrasting fabric of the same weight and textile
Don't go any wider with your triangle than the width of the original unopened pant-leg for
starters, until you get the hang of what your doing. Always practice on some
thrift store clothing first.
True Big Bell:
This is trickier to do at home. Easiest way is to buy a large square of fabric,
either matching or contrasting, and I would use a weight just slightly heavier than
the original fabric.
Cut the pants you are belling off just at the top of the knee.
(Best way to mark it is to put them on, sit down, put your feet up on a
short footrest and chalk a mark at the bend in the back and side of the knee and
the top of the knee cap in the front.)
Cut your fabric carefully into a large circle, cut a single seam into the center and
open a smaller circle in the center of the larger one.
(Measure around your knee and
divide the result by 2 for the smaller circle's diameter.)
Starting front and center, carefully stitch the round of fabric to the cut-off pant-leg.
First to the inside of the leg, then to the outside of the leg.
DON'T fully close the back of the leg until you have put them on to check the
hang of the fabric and the drape of the bell. You MAY need to take the bell in a little
at the back of the leg to set the seam straight up the back of the leg, by cutting out
a quarter inch or a little wider strip of fabric straight up on both sides of the bell seam.
You WILL need an extra set of eyes and hand to do this and pin the bell
at the back of the leg into the proper position.
Finish your stitching at the knee and the seam down the back of the leg.
Hem the bells using bias tape on the inside bottom of the bell, or simply turn the pants inside
out, fold the hem and press it it all the way around with an iron,
Tack it into place using 3 to 4 inch pieces of wide scotch tape and stitch it right over the
tape, Then pull the tape pieces off.