Framing an encaustic painting should begin when deciding and preparing what to paint on. Listed below are a few of the common choices for surfaces and how to prepare them for framing- before you begin your painting.
Plywood Panel: This is my preferred choice for surfaces; relatively inexpensive, stable, and easily available. Commercial panels are often made of cradled masonite or similar product; however, choosing a quality plywood is often a lot less expensive and doesn't require the cradle. The disadvantage comes when painting large, it weighs more than cradled panels equal in size.
Preparation is simple, just cut to size. There is no need to do anything else; except choosing a stable piece of wood. Cleaning (sanding edges, etc.) the panel up is suggested but not necessary. If you prefer not to frame your panel it is suggested that you sand the exposed edges and make sure the panel you have chosen has no (unintentional) major defects that would distract from the art.
I prefer to alter my panels; allowing the painted surface to be free of the frame; however this requires a circular saw and some light woodworking skill. Additionally this will require a deeper frame which I also make myself. But, if you lack the ability to custom make your panels and frames, this doesn't mean relying on expensive commercial product (e.g. cradled panels).
Cradled Panels: This type of panel generally frames up the same as plywood and comes in many brands, types, uses and purposes. They are all essentially the same, yet may employ another material or ground; paper, clay, gesso, etcetera are all examples of the additional layer. It is good to note that cradled panels often come in different depths or thicknesses. The depth may vary and is often superficial, acting as the body of the painting; often left bare or unframed. Additionally, many artists choose to paint this deep edge to give their painting some three dimensionality; but this is not recommended for encaustic- or in my opinion, in any painting medium for that matter. The reason being: the edge is a very fragile area and unless great measures are taken to protect this edge during transportation, storage, or what-not- it can be extremely easy to damage. Lastly, be wary of this product, cradles are often made of quality lumber, but the surface (unless specified to be made from a sound hardboard product) can often be masonite or other composite that have their own issues (check with the manufacturer). When making your own panels, choose plywood over a composite unless you are aware of the facts/details in the specified product. For more info on masonite or other composites read Wood (Includes MDF, Masonite, etc.)
Remember if you choose not to alter your panel and you will be framing it, that a traditional frame with a rabbet will touch the surface of the painting about 1/4 of an inch around the edge; depending on the frame. Frames without a rabbet will require you to clean the edge prior to framing.