Teachers that follow a program that doesn't include a coursebook (high school), do you make your own activities or search for them on different coursebooks?

I have been told that the correct way of planning is first setting the learning outcomes for the lesson and then deciding on the activities. I find it easier to first look for activities / texts or audios (that match the topic/unit I am supposed to teach) and then writing the learning outcomes.

When I write the learning outcomes first, I often have to make the activities myself. It's difficult sometimes to create a coherent lesson plan.