But you could build something similar to the fortress on the right first and expand later. That's what I did. I made the fortress before I had the stone cutter. Just find a suitably sized island close to shore and raise walls with the hoe there. :)

You'll probably need stone to raise your seaside fundament high enough. The hoe alone didn't suffice for me.

That's clever I have to say! As soon as I leave the mountains I'm going to build something similar. Though I might wait until I have stone available.