Improvised indoor greenhouse. Amazingly my wife did not strangle me when she came home and saw it.
Small grow light [too small and too high], in a south facing window, 40w appliance light for heat (located below humidity tray to promote humidity), sheet pan with gravel humidity tray, and plastic paint tarp .
Not a setup I would recommend but it was a desperation solution where I needed light, heat, and humidity for some tropicals (house humidity is often single digits), and had a very small budget. So far it seems been working. The Scheffleras seem to love it.
Safety warning: An unprotected incandescent light near plastic sheet is a recipe for a fire! Don't do it!
Nothing in there is Bonsai yet...maybe two pre-bonsai if you are feeling generous.