What you'll need:
Flowers or Greenery... obvi. I used a combination of stems from the florist and yard clippings. (And the neighbor's yard clippings)
Vase (or vaase) - the type and height of your flowers should be taken into account when choosing the type and height of your vaase. I was always afraid of "wide mouth" vases because it was more difficult to arrange the flowers, but they are the best type of vase for this "technique." That was a very Bennett Brauer sentence with all them quotations.
Double sided tape ( I used washi tape in the photos so that it would photograph better but I DO NOT RECOMMEND IT. I repeat. Do not use washi tape. It was a horrible mistake and collapsed after a couple stems. I have used one sided tape also and it was okay, but really the double sided is the bomb.com)
Fill your vase 1/3 to 1/2 with water.
Create a lattice with the double sided tape. IGNORE THE WASHI TAPE SHOWN. Horrible decision.
Trim off any extra tape around the edges.
Fill in the stems using the squares as a guide. I generally put shorter stems around the outside or any filler/greens and then try to space out my colors and use the tallest stems toward the center. There really is no right way. You can move them around and play with them until you get it how you like. My best suggestions is to not give up. About halfway through I always think to myself, Well this looks like some shit. But then I power through and am almost always happy with the end result. Sorry I forgot to take photos of me filling in the flowers.