Install/OnPrem/Solr/PreInstalled/custom-solrHTTP.json

{
    "Parameters": {
        "SolrUrl": {
            "Type": "string",
            "Description": "The Solr instance url."
        },
        "CorePrefix": {
            "Type": "string",
            "Description": "The prefix for each of the created indexes."
        },
        "CoreName": {
            "Type": "string",
            "Description": "Name of custom core."
        }
    },
    "Variables": {
        "Custom.Name": "[concat(parameter('CorePrefix'), '_', parameter('CoreName'))]"
    },
    "Tasks": {
        "CreateCustomSolrCore": {
            "Type": "ManageSolrCore",
            "Params": {
                "Action": "Create",
                "Address": "[parameter('SolrUrl')]",
                "Arguments": {
                    "name": "[variable('Custom.Name')]"
                }
            }
        }
    }
}