I like designing my breakouts in Google Sites. They are really easy to use and open up all sorts of possibilities, especially designing a nonlinear escape room, and they are more visually appealing.
If you are looking for a really simple design, you can use a Google Form and have your links embedded there. Using this method leads your students through the breakout whereas the Site option can force students to explore more.
Don't forget to have any puzzle sites you embed checked for student access before using them.
*** One drawback is that G Sites open every link in a new tab. There's no fix for that yet. So I try to include the tip that they can close out tabs as they work.
Getting Started
Topics - sometimes teachers will ask for a specific topic. Other times, I will get an idea for a puzzle and approach the teachers to see if they are interested (usually they are thrilled to have someone give them fresh ideas). The more challenging your puzzles, the more you need to narrow your topic so kids have time to complete it.
Start with the outcomes. What do you or the teacher want the kids to get out of the exercise?
Once you have that, the fun begins. Start designing your clues, diagrams, puzzles, locks, etc. This isn't a linear process for me. I play around with different tools to find which puzzles work best for each item.
Google Slides & Drawings are your best friends! You can create layered images with embedded links to guide students around. Here's an example of one: Geometry Library
Have hints ready to go. Groups will get stuck, so be ready to hop in and give them some guidance. It helps to have a set of hints ready to go before you run the exercise.