For the ricochet we drop the bow onto the string and lift it again on the last note in order to be able to start the next group of ricochet notes. The drop comes from the upper arm and from the wrist and finger joints. A fluid upper arm movement with flexibility of all the joints of the right arm (base knuckles, wrist, elbow and should joint) helps control the stroke.
Think about the best height to drop from, the best part of the bow to use and how long each ricochet stroke is. Here the slow tempo means we play relatively low in the bow and try to use quite a long stroke for each ricochet note.