full "page" images with text reflow

Hi all!
New here. Long time book production person, recently turned freelance book designer. while I'm an expert on the print size, ebooks are still a hazy mystery.

I do all my typesetting for print in Indesign, and have had ok luck exporting to epub so far, but have run into a problem:

How can I get text to reflow "around" a full page image? There are some images in this book I can treat as blocks, but most are meant to be on a facing page. Is it a sizing issue? A coding issue?

If anyone has advice on the InDesign end, or a coding tip for editing it in Sigil, that would be wonderful.

Thanks!!
Peggy
Pilcrow&Stanza / book design and production