I don't think there's a way to do this on a maple fingerboard, so I never do those, but on an unlacquered fingerboard (I've done rosewood, pau ferro, and ebony boards) there are a few methods. I used to use a screwdriver shaft to compress the wood at the edge of the fingerboard to round it off, however I now favour using an extra fine sanding pad (eg https://amzn.to/3sFbdxl) This is a much quicker job and an additional benefit of this is that it also rounds off the edges on the frets making them extra comfy on the fingers. Taking the neck off the guitar/bass to do this makes it easier. I've done this on instruments ranging in cost from £100 to £1200 and have always been pleased with the results.
Update: this is the exact pad I have most recently used, a Bosch superfine -> https://amzn.to/46gIM6B