Check out forum.woodenboat.com to read from a lot of amateurs taking on the project, just be warned that the rabbit hole is alluring and very deep.

It's typically not recommended to self-design, the physics gets technical and there are a lot of free working plans out there including by famous naval architects.

Most people start out with simpler designs using plywood and fiberglass but, due to my aforementioned disdain for a lot of modern approaches, I personally went with a traditional oak frame, cedar plank, copper rivet construction. It is very time consuming but I'm enjoying the journey. I chose a flat-bottomed sail boat design (dory) to make it a little easier on myself.

There are endless variations on the concept of a "wooden vessel that can be propelled through water" idea so it really depends on your interests and tastes. It's a "form follows function" situation too, so you also need to consider your use case -- engine, oar, sail; ocean, river, lake; etc.