WISP without DHCP, use as WISP 'modem'

I would like to use the Slate as a temporary ‘manual failover’ device using WISP. In this case I wouldn’t want to use the Slate as a router but just as an LTE modem of sorts. If I turn off DHCP on the LAN so can no longer hit the internet, is there a way to bind the WWAN to the LAN in this way, without serving addresses but providing internet?

I am by no means a network expert so any advice is appreciated!

Are you connecting a USB modem to slate? You mentioned about LTE modem.

When setting up Extender/WDS, Slate does not enable DHCP. But this is generally do not work with USB modems.

No, I am not connecting a modem to the slate. I want to use the Slate as a modem of sorts using WISP mode but without it serving addresses and routing.

I see. You need to use extender mode. Go to more settings, network mode and set it up.