Finding abandoned carrot field or plaice spot near swamp are probably most viable for a new player.
If you have barley or wheat, you can bake Blueberry Pie.
Assuming wiki's information of Plaice is correct, you need to find a swamp that is next to or close to a river or lake with node for Plaice. This will require some testing but will likely yield some other fish as well that you can easily stockpile for future use. Worth noting that type of fish you get can vary depending on the time of (in-game, roughly 8 RL hours long) day. If you don't see any fish jumping around, don't waste your time as it indicates there are no fish currently in local node.
I ended up getting inspired to expand wiki page for
plaice. Doubt it is still perfect, but if a new player reads that and the Fishing page, they should have decent instructions on how to catch plaice.