Fold the cloth in 4 layers and then you take the measurements.
a-b, c-d - 1/4 hip measurement + 5"
a-c, b-d - pajama length + 3.5"
j-k - ankle loose + 1" ( it is loose at the ankle so i have taken the measurment
j-c - folding 1"
a- e - waist belt ( double width of the belt ) width + 1/2''
e- j - pajama original length
b-g - 3/4"
f- h - crotch/3
the measurements are including the stitches.
I have not attached the waist belt separately so my elastic casing is including the pajama measurement which is shown as marking 'a-e' , if you want to attach the belt separately then you have to take the length measurement as original length + 1.5 inch ( that is e-c ) and the belt is double the width + 1". Cut the fabric from bottom to crotch and crotch to g.
The sewing method is same as legging