Statistics Canada released a nice 4 minute animated video showing how GDP is calculated using the value-added approach.
It begins with the definition of GDP as “The value of output less intermediate consumption plus any taxes less subsidies on products not already included in the value of output.” But the definition is immediately shortened to “The value of output less intermediate consumption,” which is a good example of an initial simplifying assumption in a model.
If you are covering the value-added approach in Macroeconomics for Life (Chapter 6.3), show this video first.