(After 13 days, no one has answered this question, so I researched it myself.)
According to Skylab: A Guidebook,
Solar energy is the prime source of electric power on Skylab. Two systems of solar-electric cell arrays, one on the Workshop [OWS] and one on the Apollo Telescope Mount [ATM], will be deployed after the Skylab cluster has reached orbit. The OWS system consists of two wing-like structures which are folded and packed against the Workshop wall during ascent. The ATM system, folded in a similar way during ascent, deploys in the shape of a four-bladed windmill (Fig. 131).
p. 107
The four wings of the ATM solar array are each composed of 4½ flat solar panels. The panels are connected end-to-end by hinges and folded accordion-style before launch. The inner-most panels are attached to the ATM by another hinge, and folded down before launch. The ATM is positioned upright at the top of the launch stack:
Once in orbit, the payload shroud is ejected. The ATM rotates 90 degrees on a pivot (clockwise on the picture below, annotations mine).
Then the wings are extended by a scissor mechanism. The panels themselves form one side of each scissor. The drawing below is poor quality, but you can see the accordion pleating of the wings:
Each workshop solar wing extends from a beam, which is attached with a hinge near the forward end of the orbital workshop. At launch, the beam is folded down and becomes part of the outer trimline of the vehicle. Various sources specify that the solar panels are somehow folded under the beam before launch, but no source explains or shows exactly how. My educated guess is below.
An accident during the ascent of the station tore off wing #2, and jammed wing #1. When the first crew arrived, they took the following picture of wing #1 (annotations mine):
The National Air and Space Museum has a copy of the orbital workshop and its solar array:
Each wing is made of 3 columns of flat solar panels. I believe these are attached end-to-end by hinges, and folded accordion-style before launch. There are also structures on the back side of the wings; I believe these are scissor extenders. You can see these in both pictures above. This would account for the claim they are "folded in a similar way" to the ATM arrays: both have accordion-folded solar panels and scissor extenders. However, unlike the ATM arrays, the the scissor extenders on the workshop arrays are a separate structure from the solar panels.
(Something else I learned during this research was where the control moment gyros were located. I had always assumed they were somewhere in the body of the station. They are actually located in the Apollo Telescope Mount -- which makes some sense because it is the part of the station that demands the most precise attitude control.)
