You can use the noun planning to talk about the process of making a plan. Your elaborate tree house project will require hours of planning before you hammer a single nail into a piece of wood.
Planning is the act of getting ready for something to happen — you might find that the planning for the prom and the excitement it brings is as fun as the event itself. During planning for any event, you figure out what things you will need, how long it will take, and what you will do if anything goes wrong. For a cook, planning might include finding and measuring all ingredients, gathering the pots and pans they will need, even checking that the stove works!