Strengthening. 8-12 weeks of quality, graded strength work is the best evidence we have to get plantar fasciitis better. We want to strengthen both the calf, soleus (muscle behind the calf) and the foot muscles.
Not only do we need to strengthen these muscles with a range of calf raise (straight leg, bent leg, toe under towel), we also want to add 10-20% of our body weight to these exercises. Not only does this get us stronger it adds a buffer for the next time our load increases and can serve as a long term preventative measure to keep your plantar fasciitis away.