You put a book into your crafting grid and get a linking book. This links that book to where you're standing upon creating that book, you can make a portal of Crystal blocks. The size and shape don't matter, so long as you slap on a book receptacle somewhere and put the linking book of where you want to go into it.this may sound silly but..... what is mystcraft and how do you get portals?
He's trying to run a wheat farm, not NASA. Put some peat engines on that farm and be done with it ;p