I've watched the first video you psted last night. While it does a good job explaining the overall process from modeling through CAM to a final prouct, the Fusion 360 related modeling part exhibits a number of shortcomings and not recommended work practices. It may be ok for this simple shelf, however for more complex designs it won't sufice. The two main hints Mark has already provided.
- The first thing the vast majority of people should to is to create a component and activate it. For newly created components the activation is automatic. If you have more components, beore eiting one, activate it.
- thist will ensure that all objects created, sketches, joint origins, construction geomery etc. are created in that component.
- on actvating a component, the timeline on the bottom of the screen willget filetered to show only those operation pertaining to that component.
- Name yoor stuff. Everthing that you might want to get back and eidit should have a distinctive name so you can easily identify it. Sketch 1,3,4 is not very desriptive 😉
3. The work practice employeed in that video is in general that you make a master, or skeleton sketch that everything is referenced off. That can be a sketch does not need to be in a component an can reside in the top level sketch folder. However, For the sake of better organization I'd not use that sketch to directly extrude the first component from.
I'd create an empty component, start a sketch there and then project only the needed sketch elements from the master sketch into the new sketch and hten use that to extrude the first component.
Then I'd make a second component and to the same thing. This is a little more work, but it really keeps things better organized, and will certainly help down the road.