Export your design from Polotno Studio as JSON, then paste the exported JSON directly into BuildOnce's import dialog — there's no file upload for this source, just pasted text.

{"width": 1080, "height": 1080, "pages": []...}

BuildOnce reads the Polotno document directly — text, images and shapes on every page carry over, and text/image layers become editable template variables automatically.

Pasted text is capped at 2 MB, well past what any real export needs.