You simply need to think of a place you know very well (child house for example) and for instance imagining going from the front door to your bedroom.
On the way to the front door you see a carpet on your doorstep instead of a door mat, when you look closer to the carpet, you see that there is a horse on it. But that's not all, something funny is going on, a dog is riding the horse! When you look up, you see a giant cat sitting behind the window. Oh no, it is not a cat! It is a lion! and his manes are on fire.
Probably just from reading a story like this, you already envision something. By making it a bit funny or crazy, your mind will easily remember it.
It may need some practice, and at first you definately want to write down the words for back up. It is also important to walk through the memory palace once in a while to keep the memory fresh.
This sounds very complicated. The thing is this is way too much words. I really dont think many people here would remember the 12 world phrase. Let say they do... now you have to make sure you got it all in the right order.
that is the way to memorize things like this but i don't think it is a good idea in case of a seed because first of all it is possible that you will forget about the actual words and be confused that was it "carpet" or door"mat".
besides it is hard to make the connection for the seed of 12-25 words for example like this:
constant forest adore false green weave stop guy fur freeze giggle clock