Static front page

Have you selected and existing page? To use that, you have to create new page from the wordpress dashboard, and then asign it from the reading settings.

By white you mean whole screen is white (no logo, navigation) or no content, but the theme is there?

If first, just check if you have home.php and if it has content.
Secound check with debugger if you have errors.
Third, if for the page you created, you use some template, that migh bt empty or promt error, it can be empty page again.

In any cases, you must have your debug on.

made a custom theme

a static front page would use (in this order of preference) front-page.php, page.php. index.php ( https://codex.www.ads-software.com/Template_Hierarchy )

which of those files are in your site?
what is the code of the one used for the front page?

about DEBUG https://codex.www.ads-software.com/Debugging_in_WordPress

Thanks.