Can I make a landing page without the header and footer?

Yes. Each page has its own layout options:

1. Go to Content → All Pages and edit the page, or click + Add Page.
2. In the Layout box on the right, tick No header and/or No footer.
3. Click Save changes (or Create page for a new one).

The page then shows without your site header or footer, while the rest of the store is unchanged. Build the content with Normal Builder and Open Builder →. Since there is no menu, add a clear button that links to your product or to checkout.