Only Ethernet Bridge(via LACP) as transparent Firewall

Hello,

I have 2 switches in the same network (192.168.0.x) connected (uplink with 2 ports, via LACP).
I would now like to switch a RB750gr-3 router as a transparent firewall in between.

QuickSet is probably not suitable ..?
Firmware: 6.43.4

Does anyone have a helpful sample configuration?

Thanks for your help