Use a non-magnetic stainless steel shaped strainer as support and place in a glass, ceramic or aluminum bowl filled with cooking oil (hydrogenated high smoke point) or sand (not so good inmho)
You could always use a retort stand coupled with retort clamps and boss-head clamps.
Swim usually just uses a clamp around the neck of the flask to hold it so the bottom of it just touches the top of the hot plate. This works fine with a stir bar. Swim has also used aluminum blocks with round impressions in it. In order to get proper temperature control, swim uses an oil bath with a temperature regulator (an electronic thermometer thing that hooks up to the hot plate and has a probe that goes into the oil bath and keeps the oil at a specific temp).