Yeah it is pretty easy, and I get a feeling of satisfaction when it comes out perfect...my mom actually taught me when I was a kid. She made all kinds of cool splices. I do mostly basic stuff.
I have a slip and an mooring. Moorings are great but...you only have one line to the mooring and you are probably not going out to board your boat in a hurricane to check the line so that line or two you have on there has to be ball buster good. I would just buy one of those yellow jacketed well made mooring pendants like :
Yale Maxi-Moor II Mooring Pendant Since most lines fail from chafing, make sure it is protected from rubbing against anything.
It is always nice to have some custom lines but you need to be able to sleep well when you hear the wind howling this summer. So I would just buy what you need for now.
practice your splicing in the off season. You should buy a fid kit that has both styles of fid (for braid and Swedish for stranded, you can do make some splices in three strand lines without fids but they are cheap and the job goes a lot easier. You can even make your own fid) Also if you have big thick fingers with no nails you really need a fid.
Likwid: That is an insane dog lease. You probably could perform boat/truck rescue service with that .