How do I go about clearing land for farming above ground? I managed to throw down some 5x5 plots but they're a little scattered. I like it when the plot is perfectly filled, not full of gaps because of pebbles or saplings or dead monarch remains or whatever else is around
Saplings/plants: cut and gather them, accordingly
'Pebbles' (boulders?): Smoothing out a boulder gives you rock, not sure you can do anything with that.
Other dead remains: Not sure if I've ever had a problem with 'stuff' on the ground, especially cat-caught stuff. It'll most likely be a problem with the underlying ground.
When it comes to farms, these days I tend to make them all at Z-1, where the soil allows with the "open air" ones built via channelling[1] and/or ramps/ramp-removal, then the appropriate communications made with the underground part of the complex (from the field side if the ramp removal dwarf has trapped himself down there, which is a good incentive to getting the job done
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With the exception of having to make sure you don't create undue cave-ins, it streamlines things quite well.
Alternately, use any old rock surface that doesn't have problematic features (without boulders, or boulders that have been smoothed) and wet it by one of a number of possible methods (suitable water supply allowing) to make it a viable field across the whole
Better Solutions Are Probably Available.
[1] Usually by designating:
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That's for 3x3, adjust as appropriate for bigger intended fields. i.e. designated the 'cross', formed by the two major diagonals then the remaining 'edge' 4 from the central nine, then the remaining 'edge' 12 from the 5x5's outer 16, so that at all times you're able to access the channellable squares from adjacent spots and (if you've already dug underneath) you don't leave any cave-in potentials. There are other ways (e.g. 'stripe'-mining it) but I tend to like this method.