Mix or Match?

My class has been working on a sequential paragraph called "How to Carve a Pumpkin." Yesterday they wrote a variety of possible beginnings (question, dialogue, onomatopoeia, surprise statement, etc.) and endings. They've already drafted the steps, so today's the day they'll put it all together. But here's the question:

Should students mix or match their beginnings and endings?

It was apparent yesterday that many students thought that if they began with a question, they had to end with the answer, and if they began with onomatopoeia, they had to end with onomatopoeia too. Since we use a sandwich analogy for our paragraphs, they have heard me say, "You can't put a hot dog bun on top and a hamburger bun on the bottom." But is that what I really mean?

To help them focus on how the conclusion should logically follow the introduction, we'll try this activity first. 

Exploring the writing process really benefits my students, but sometimes, when we break the writing into little pieces, it's hard to put the whole thing back together again to establish a smooth, flowing piece. How do you address this quandary in your classroom? Please comment and let me know.