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The work done in assembling a continuous system having some charge density is given as the $$W=\frac{\epsilon_{0}}{2} \int E^{2} d \tau$$ which is always positive.

Does this mean no matter what configuration of shape and charge density I choose, the work to assemble will always be positive?

In the discrete case of point charges this isn't the case, we may have positive or negative work depending on the configuration

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Electric field energy would be an integral of energy density over volume. If we assume that the universe is electrically neutral, then all electric fields are a combination of dipole fields. You do positive work, which goes into field energy, when you separate the + and – charges of a dipole, but negative work if you bring them back toward each other. (The field energy is always positive, but it may be increasing or decreasing.)

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