I searched the designer on Ravelry and found them:
http://www.ravelry.com/patterns/library/studio-shorts
The pattern is free.
Here's what it says for 'attach legs at hip':
ATTACH LEGS AT HIP (Both Versions)
Line up legs and place live sts from both onto 24” needle. Leave 15[16, 17, 18, 19,
20, 21, 22] sts from each leg on scrap yarns, aligned at the crotch. These will be
connected later. Pm at the front center leg join (called fm). Count the number of sts
on the needles from one of the legs and divide that number by two (number x).
Count x sts from fm and pm. This marker will be the left hip (called lhm), which
marks the beg of the rnds. Slip sts from one needle to the other until lhm is at the
beg of the rnd. Count x sts from fm in the other direction, pm, and this will be the
right hip (called rhm). See photos for details.