Thanks for the question! Yeah actually as DavidA3D mentioned it would probably be best to find maybe a teammate or a template but you do bring up a good point, Mario Maker could be helpful if you wanted to make a level and then recreate the layout in the template, I think that could work well actually! Here's a little step-by-step tutorial that could be helpful too: https://mozdevs.github.io/html5-games-workshop/en/guides/platformer/start-here/
I hope that helps and best of luck!!!