在ARM模板中部署App Service和slots时，可以使用以下示例代码来解决问题：

1. 定义App Service和slots资源：

{
  "name": "[variables('appServiceName')]",
  "type": "Microsoft.Web/sites",
  "apiVersion": "2016-08-01",
  "location": "[parameters('location')]",
  "dependsOn": [],
  "properties": {
    "serverFarmId": "[resourceId('Microsoft.Web/serverfarms', variables('appServicePlanName'))]",
    "siteConfig": {
      "appSettings": [
        {
          "name": "SLOT_NAME",
          "value": "[variables('slotName')]"
        }
      ],
      "alwaysOn": true
    }
  }
},
{
  "name": "[variables('appServiceName')/slots/default]",
  "type": "Microsoft.Web/sites/slots",
  "apiVersion": "2016-08-01",
  "location": "[parameters('location')]",
  "dependsOn": [
    "[resourceId('Microsoft.Web/sites', variables('appServiceName'))]"
  ],
  "properties": {
    "serverFarmId": "[resourceId('Microsoft.Web/serverfarms', variables('appServicePlanName'))]",
    "siteConfig": {
      "appSettings": [
        {
          "name": "SLOT_NAME",
          "value": "default"
        }
      ],
      "alwaysOn": true
    }
  }
}

2. 定义App Service计划：

{
  "name": "[variables('appServicePlanName')]",
  "type": "Microsoft.Web/serverfarms",
  "apiVersion": "2018-02-01",
  "location": "[parameters('location')]",
  "sku": {
    "name": "[parameters('appServicePlanSku')]",
    "tier": "[parameters('appServicePlanTier')]",
    "size": "[parameters('appServicePlanSize')]"
  },
  "properties": {
    "name": "[variables('appServicePlanName')]",
    "workerSize": "[parameters('appServicePlanWorkerSize')]"
  }
}

3. 在参数部分定义所需参数：

"parameters": {
  "location": {
    "type": "string",
    "defaultValue": "China North",
    "metadata": {
      "description": "The location of the resources."
    }
  },
  "appServicePlanSku": {
    "type": "string",
    "defaultValue": "B1",
    "metadata": {
      "description": "The SKU of the App Service Plan."
    }
  },
  "appServicePlanTier": {
    "type": "string",
    "defaultValue": "Basic",
    "metadata": {
      "description": "The tier of the App Service Plan."
    }
  },
  "appServicePlanSize": {
    "type": "string",
    "defaultValue": "B1",
    "metadata": {
      "description": "The size of the App Service Plan."
    }
  },
  "appServicePlanWorkerSize": {
    "type": "string",
    "defaultValue": "0",
    "metadata": {
      "description": "The worker size of the App Service Plan."
    }
  }
}

以上示例代码可以帮助您在ARM模板中部署App Service和slots，并设置相应的配置。您可以根据自己的需求进行调整和修改。