Double-sided index cards printed on letter paper

I’d like to print multiple index cards on a single sheet of letter paper (4"x6" specifically, so 2 a page is fine) but have text that I insert come out double-sided when they’re printed duplex. I’ve tried with both regular 4x6 pages and then printing multiple to a page, but those came out too big (about half of a letter page in size instead. I also tried using the index card template, but then everything came out too small when I tried to duplex print them.

There are options in:

Menu/File/Print - Page layout.

Or try exporting first to PDF, the pdf readers are used to deal well with this situations.