TL;DR(De)construct dense areas faster by having personal robots do the closest thing first, since you can then move around and keep flight distances short.
What ?Construction bots from your personal roboports have a clumsy order in which they select construction tasks. This causes long flight times. For deconstruction, you can do better by deconstructing small patches and moving around, thereby keeping the flight distances short. A quick demonstration (gfycat cut off the video though):
(takes about 40 seconds)
(takes about 20 seconds)