Hello Dimas
The configuration doesn’t change much if you add more spine switches. The Leaf switch configurations remain the same. If you have two or more spine switches, you simply have to ensure that you have configured EVPN as the overlay, and that you have configured BGP using the L2VPN EVPN address family. As long as BGP has converged, your network will function.
This is an excellent exercise that you can try out in an emulator. It will definitely help you to gain a deeper understanding of the intricacies involved in VXLAN MP-BGP EVPN configurations. If you do so, let us know how you get along!
I hope this has been helpful!
Laz