Block/Stop Ukes’ striking hand before it has a chance to get to past his center.
So if uke strikes with right hand. Tori blocks with both hands, one close to wrist and one close to inside of elbow (this blocking is supposed to take Uke balance since his hand will be kept back while his body still wants to move forward, hence, upsetting his balance). The Tori does a switch grip and performs and ikkyo Ura movement and takes Uke to the gorund.

Then finish with a Gokyo pin.
For this pin the transition from the Ikkyo pin is to keep hold of uke right elbow with your left hand and slide the Ukes wrist with your right hand so the Ukes’ hand makes a vertical Z like shape. The back of Uke‘s palm will be on the ground completing the pin.