Hey this should be on by default on sg300s as all the ports are set to trunk by default if my memory is correct so you should be able to just connect 2 together, they make SMB switches like this out of the box.
Aswell if your using only vlan 1 you don't need a trunk as trunks are only for pushing more than 1 vlan down a cable at a time ,vlan 1 will be allowed on all ports as its the mgmt. vlan so there should be no issue in just connecting any 2 ports together in the switches
You cant stack sg300 that's a different concept only sg500s but you can daisy chain and your good to go
