Unfortunately there isn't an easy way around this. The A3010 was intended as a home machine and lined with the suitable peripherals of the time. Acorn felt that an IDE interface was just luxury for the home user (since games mostly ran from floppies) so they didn't waste expense on adding one.
This means that to use a hard drive, you need to use a "hard card" that fits into the podule slot. The problem is, you only get one slot and you need that for an ethernet card.
Since the TCP/IP stack is part of the latest !Boot install, you will need a HD for the stack.
If you're handy with a soldering iron, you can try building an external mini-podule slot by running some ribbon cable from the existing pins out to an external connector, but its not an easy job.
The only networking that is "built in" to Risc OS is the Econet support. Unfortunately this is no use to you as econet-to-ethernet bridges are hard as hell to obtain, and there is no Econet outlet on the A3010. Thusly, the socket to support an Econet module is not present.
So while you have Econet support in Risc OS 3.11, you don't have any means to connect hardware.
This is one of the complaints regarding Acorn's decisons on the A3010/A3020/A4000 range. The A3020 was an ideal compact machine, but without joystick ports. The A3010 had the ports, but nothing else useful
The A4000 is basically just an A3020 in a 3-box design.