This doesn't seem to be a commonly-used basic pattern. It has the advantages that it's easy to plot, there're no central front or back seams, and that you can adjust the crotch height more easily than you can with the conventional pattern.
I found this pattern to give a looser fit than the conventional pattern, but that's probably because it was the first leg-pattern I tried, and I haven't explored it much since I began to understand the conventional leg. This page needs to be updated to take differences between the front and back of the body into account.
There are two body+leg panels - one each for front and back - and two panels running up and down each side of the inside legs.
Note, if you want a more conventional gusset, where the gusset only extends a short way down the legs, you might try this one based on the one/two panel method.
- Make sure the long edge of your paper is straight, or draw a straight line close to the paper's edge. This is the central fold line.
- Plot quarters of your body circumference to one side of the central fold line, the measured distances apart, until you've plotted the crotch.
- Divide your leg circumferences by three, and plot the crotch leg measurement from the outside end of the crotch body measurement you just plotted.
- Half way along the crotch leg measurement, draw the central leg line, parallel to the central fold line.
- Plot the rest of the leg measurements equally on either side of the central leg line.
- The top of the leg may be too wide to plot as described. If so, reduce the leg width until it's about an inch away from the central fold line, and remember to add the removed width to the gusset piece (since the leg piece actually turns into two panels - the front and back - you'll need to add twice the removed width to the gusset).
- Cut the square angle at the crotch into a quarter-circle.
- Add notches at knee, hip, and waist.
The gusset is the same as the body's leg piece, except at the top, where you will need to widen it by twice whatever you reduced the body/leg piece, and lengthen it to match the quarter-circle you cut at the crotch.
Lay the gusset on top of the body's leg piece and smooth their outlines so they match, except at the top where the pieces differ.
If you choose, you can put a greater proportion of the leg circumference into either the body/leg or the gusset. Just remember that if you only use one body pattern piece, changes to it will affect two panels - the front and back - so you'll need to change the gusset twice as much.
Add notches at the knee, that matches the body/leg notches.
With suitable account taken of sleeves and zips:
- Cut two body panels on the centre fold, and two gusset panels.
- Pin the front and back panels along their outer edges with right sides together, and sew.
- Pin the left and right gusset panels together along their topmost edge with right sides together, and sew.
- Pin the edge of the gusset along the inside leg of the front panel with right sides together, and sew.
- Pin the edge of the gusset along the inside leg of the back panel with right sides together, and sew.
It's possible to put a sort of fly into this garment:
- Extend the leg gusset at the crotch by a few inches.
- For each piece, fold half the extra, wrong sides together, and sew along the edge to secure it.
- Lay the pieces both same side up with the stitching matched, but in opposite directions (as in diagram).
- Pin the overlapping edges together along each side, and sew.
- You should end up with a gusset you can use instead of the one described above, with an overlapped hole instead of a plain seam.