What is looks like: Your dog goes in and out through your legs as you walk.
I would recommend a leash on your dog so you can guide them until you no longer need it. do not pull your dog simply use it as a guide. Start with your dog on the right of you, take a step with your left leg and have food in your left hand and lure your dog under your leg, once behind your knee click and reward. Once your dog is comfortable going under your legs, have treats in both hands and click each time your dog passes through your legs. Lure them under one leg, click and reward then take a step and lure them through the other leg click and reward. After a few sessions have them go under 2 times consecutively before you click and reward, then 3 times then 4 times over time. Once they can do 4 “weaves” before actually getting the reward, you do not have the food in your hand any longer. Practice without food in your hand and click and reward for one “weave” then 2, then 3, etc Give it the verbal cue ‘weave’ and you might have to put your hand, without food, to help guide them at first, if they are struggling go back a step.