It’s not that we can’t answer a beginner’s question. Generally when there is a problem getting the question answered, it’s because the person with the question hasn’t asked it clearly and has provided no examples in the form of screen shots or even SketchUp files. Answers come quickly and accurately when we aren’t made to guess at what is really going on.
Pruning from a larger block is one way to work and it is appropriate in some cases. Sometimes it makes more sense to add geometry instead of pruning. If you were to share an example file, there are many of us who would be delighted to help you out.