You can of course sand the base of any plane flat with sandpaper stuck to a pane of flat glass.

I like Rex Kruger's channel on YouTube for ways of upgrading the performance of cheaper tools. I certainly got my old Stanley No.4 into a decent shape after watching some of his videos.

Here's his playlist on planes. https://www.youtube.com/watch?v=8L07...SUAtmy8Cdua7Td