@ThomasC, Sorry! I have got Ecwid & Shopify working perfectly! Never tried Snipcart.
Reading this - https://docs.snipcart.com/v3/setup/installation, it looks straight forward - you only need to drop in three sets of code snippets.
I would put these code snippets in an Embed and position it more towards the top of your Sparkle canvas…
<link rel="preconnect" href="https://app.snipcart.com">
<link rel="preconnect" href="https://cdn.snipcart.com">
<link rel="stylesheet" href="https://cdn.snipcart.com/themes/v3.0.14/default/snipcart.css" />
I would then create a second Embed and place it towards the bottom of the Sparkle canvas…
<div hidden id="snipcart" data-api-key="YOUR_PUBLIC_API_KEY"></div>
They then suggest to get your public api key and then overwrite where it says in the code “YOUR_PUBLIC_API_KEY”
You then create your product items in Snipcart and generate a BUY NOW button and you’ll get a code snippet like…
data-item-description="High-quality replica of The Starry Night by the Dutch post-impressionist painter Vincent van Gogh."
data-item-name="The Starry Night">
Add to cart
Which you again place in an Embed and place it under your product on the Sparkle canvas.
I’m not sure if this will help, or you have already done all this but I hope it does help somewhat… good luck!
EDIT : Oh no! I just saw Duncan’s response!!! Ouch!