https://youtube.com/watch?v=EXDM2IsP7ac
And a low effort pvzxtouhou mem just manifested!
It seems most of your questions were answered.
>>/4241/
> Am I supposed to imagine a sea?
How do you imagine an island without the sea surrounding it? And yes that is supposed to work as a "barrier" and connection force. Your island needs a sort of border and the sea is the most natural border. The sea has a lot of spiritual functions but it's not important now. Even the sky is a sort of "water". Astral literally means the starry sky in one way or the other. That "sea" will sync it with the astral environment.
> What am I missing?
You have to try until it works or if it doesn't work no matter what then you have to describe at what level your visualization or tulpamancy skills at otherwise helping you is difficult.
>>/4243/
But as he said. Sigils are the same as a tulpa. You just have to charge it with your attention or energies and feel it connect to your mind. Some sigils will be easy to connect while some will be incompatible and needs other adjustments in your mind first.
> and why?
Because you are interested in it? Use it if you feel it is for (You) if not leave it.