Press your knuckles into your client’s gastrocnemius at the achilles tendon. Glide up the gastrocnemius with your knuckles as your client dorsiflexes their ankle. Rotate the foot externally to work the medial aspect of the gastrocnemius.
The soleus does not cross the knee joint, so you can get a deeper stretch to it by flexing the knee slightly to relax the gastrocnemius, then dorsiflexing your clients ankle.
Flex your clients knee and rest their ankle on a bolster or your knee to work the soleus.