Write One of Your Own!
Now that you understand what I mean, let's get to work on building your own.
For a shape poem, keep the topic simple. Much easier to write a poem about fish that looks like a fish than to write a poem about world peace that looks like world peace. So either start with something you want to write about or start with a shape you want to fill. By nature, shape poems are playful exercises, so don't attempt anything to complex or deep.
I always say free-write. Get a page and fill it. Remove the filter from your thoughts and disengage the muffler on your brain. Dump out everything you think and feel about your topic.
For the purpose of a shape poem, free-write particularly on synonyms. If you say the fish is as blue as the sky, consider other words for blue and other similes to describe the fish. Think about longer and shorter words with the same meaning. When it comes to building your final product, you'll want pieces of different sizes for construction.
Because your shape will dictate where you lines end, using these endings right is very important. Use strong enjambments, end-stops and caesuras. Not sure what they are? Review your glossary.
Just because you've reached the tail of your fish doesn't mean you have to stop at “the" in the middle of a phrase. End with strong words just like you would with any other poem. You'll need to do some juggling to do this, but just because you put words on a page in the shape of a herring doesn't mean you're successful. You still need great words arranged with power.
Your shape will also dictate a rhythm. A diamond shaped poem will start with a short line, gradually grow longer and longer before shrinking back to a short line. Make sure this music works for your poem.
Take all the bits and pieces from your free-write and compose the long and short ones just the right way. Hopefully you can mess with the order of your lines without disturbing the story. Scan the stresses in your first draft to see if the beats are building the right song.
Making it Fit
The most challenging part is shaping a quality poem to fill your mold. This is where you want to have copious amounts of material from your free write. A line too short? Replace a word with a longer synonym. Squeeze in another image.
You also can play with sentence structure and grammar to make things fit. Change tenses. If “I was going to the lake" is too long, try “I went to the lake" or “went to the lake".
Also, use the sculptor's idea that a statue is inside the block of stone already. All the artist does is remove the extra material. Over-write the poem then shrink each line until it fits your shape. Trim the diction back to its fundamental muscles. Better to tighten than to add flab.
Back in elementary school, I remember our teacher asking us to tear a piece of paper, making sure the edge was wavy and ragged. Then we were challenged to write a poem to fit the irregular shape of paper. Try it. It will make you adept at crafting lines of varying length.
Another challenge is to write a poem to fit a found object, perhaps a scrap of cardboard or piece of wood. If the object is difficult to write on, cut a piece of paper to fit. Write a poem to fit the object, in shape and meaning, then glue it on.