Hi Pau,
I'm having a similar issue with 'sliceProps' not working at all. I just wanted to check whether this was possible when using Gatsby?
Should the below work? I'm a bit confused why this isn't a built-in feature as it's a pretty common need to pass properties to components.
const test = { message: "testing"};
return (
<Layout isHomepage={false} settings={settings} body={body}>
<Seo title={document_display_name.text} />
<SliceZone slices={body} components={components} sliceProps={test}/>
</Layout>
)