If you want to set the homepage for your custom domain, you go to the Team admin panel.
Instructions
In the Pages sidebar, click Settings next to your team's name.
Now select the fourth option Team panel & SSO.
The second option there, Panel start page, offers a dropdown menu, where you can select the homepage for your entire team.
You can only select pages you've shared publicly. Only these pages are accessible without a Start.me account.
If this box is empty, even though you have multiple pages, you might have to change the sharing settings first.
The start page you select here, will be the first one your users will see when they enter the address of your custom domain.
Click Save settings to confirm. It might take several minutes to implement your changes.