To deploy linked, clone-based Microsoft RDS servers using Horizon, you will first need to create a customization specification in vCenter. Customization specifications are used to customize the Windows OS during the deployment process, and include information such as the product key, local administrator passwords, and other basic information.

The VMware vSphere documentation section titled "Creating and Managing Customization Specifications" (https://docs.vmware.com/en/VMware-vSphere/6.7/vsphere-esxi-vcenter-server-671-virtual-machine-admin-guide.pdf) provides details on how to create and manage customization specifications in vCenter. The only customization specification setting explicitly required by Horizon in order to deploy RDS servers is the Computer Name setting; it should be set to Use the virtual machine name.