Megacon Games have a youtube video that details how to fix warped plastic miniatures, which is the technique I used here.
The technique demonstrated in the video can also be used for basic conversion work on plastic models too!
Here's the process I used for this fixing this particular model (note that I have not glued the model to the base yet):
- Remove the model from the slotted base
- Dunk the model into the hot water, from the shins down, for 10-20 seconds
- Take the model out of the hot water, and reinsert it back into the slotted base
- Bend the model so that it has the lean you want
- Run the model, still attached to the base, under cold running tap water for 10-20 seconds