I'd love to be able to credit the original photographer and/or gardener for this image, but I'm afraid that will remain unknown for now. I found this striking faux fire under a boiling pot of posies on Pinterest, but the link to the original is blocked due to potential problems with that site. If you know who the photo belongs to, please drop me a line.
This one is self-explanatory. The cauldron is filled with a plant pot with white flowers to resemble bubbles. I'm not sure what kind of flowers are in this pot, but I'd add sweet alyssum to the pot to give it the illusion it is boiling over.
The real charm here lies in the surrounding the pot with sticks of firewood and then planting yellow and red flowers to simulate flames. The petals of the yellow daisies add a nice touch. I'm not sure what the red flowers are, but they look like red nicotiana to me. You could also use dwarf red petunias. Dwarf cosmos in shades of red, orange and yellow or dwarf marigolds are also good options for achieving the simulated fire.
Until Next Time . . . HAPPY GARDENING!