To "knock out" a plant or to remove it from its pot for inspection or repot ting, hold the main stem between the fingers of one hand and the pot in other. Watering an hour in advance will make the job easier.
Without changing your grip on plant or pot, turn them upside down and knock the rim sharply once or twice on the edge of a workbench. The impact will jar the plant loose from the pot with roots and soil intact.
Pull the pot up and way, allowing the plant to slide out while you hold it in your lower hand. You can now check to see whether the roots have grown enough so that the plant needs a larger pot or root pruning.