How did Locke explain the formation of complex ideas from simple ideas?

In his work An Essay Concerning Human Understanding, John Locke rejected the doctrine of innate ideas, arguing instead that the human mind begins as a blank slate, or tabula rasa, and acquires all materials of knowledge through experience.123

Locke categorized all ideas as either simple or complex:

• Simple Ideas: These are the basic building blocks of knowledge, derived directly from sense experience (such as the color, shape, or texture of an object) or reflection (the mind’s awareness of its own operations, like thinking or feeling). Simple ideas cannot be broken down into anything more basic.13
• Complex Ideas: These are formed by the mind through the process of "compounding," where it combines various simple and complex ideas together.13

For example, the complex idea of a "snowball" is constructed by the mind by combining the simple ideas of whiteness, roundness, and solidity. Consequently, Locke argued that philosophical inquiry should involve analyzing complex ideas by breaking them down into their constituent simple parts to clarify their meaning.13