How would I go about making a poem out of Lord of the Flies?
If your teacher has not specified that you must create a certain style of poem for this assignment, I would suggest that you consider writing a bio poem. I use this style of poem in conjunction with different stories and novels that I teach, and my students seem to enjoy writing them. I have included a link to a website that gives examples and line-by-line instructions for creating a bio poem.
As you write, try to imagine yourself as the character you're writing about. Doing so will give you insight into details that you may choose to include and will help you to interpret events, settings, and other characters in a manner relatively true to the character you choose. Including an appropriate, colorful background (if allowed by your instructor) will add to the power of your written words.