Hi @randomsky
Did you add body in HTTP request like below
{
"request": {
"__metadata": {
"type": "SP.SPSiteCreationRequest"
},
"Title": "New Site",
"Url": "https://contoso.sharepoint.com/sites/NewSite",
"Description": "This is a new site",
"SiteDesignId": "6142d2a0-63a5-4ba0-aede-d9fefca2c767",
"WebTemplate": "STS#3",
"TimeZoneId": 4,
"OwnerIdentifier": "object-id-of-security-group"
}
}
Add the object id in OwnerIdentifier field
Hope this helps 🙂