Ok but you need to understand that even though you want it to be a full page layout, it still needs to be saved as a Section file.
Still not advisable but if everything is correctly formatted:
So if it’s truly a Liquid file, go to the code editor, right click on Sections and create a new file. Name it, and put “.liquid” at the end. The new file will open. Make sure it’s blank. Then paste your Liquid code and save. It must have a {% schema %} block at the bottom.
Once that is done, you can go back to the theme editor, create a new Template, and add the section and remove any old ones you don’t want.
Then you can assign the Page to the new template in Admin.