This is a combination throw off a missed foot sweep. It can be used as a set-up for an ashi guruma or an o guruma, based on leg placment. An important point to remember in Judo gurumas is that the foot/leg is used to create a static point while the hands and body motion provide the impetus for the throw.
Begin with standard judo grips.
Tori attempts an advancing double foot sweep. Uke's reaction is the key to this entry.
Uke steps back to avoid the sweep. Tori continues steping across uke's body placeing the left down with the toes pointed perpendicular to uke's hips (or as close as possible).
As soon as tori's left foot gets traction the hips should pivot left bringing the right leg through and across uke's hips for O-guruma, or across uke's lower thigh/knee for Ashi-guruma.
Tori continues the momentum from the intial pivot and uses his leg to block uke's hip from advancing.