  The 2D power spectrum is a cornerstone of the modern toolkit for analysis of
the low-frequency radio interferometric observations of the 21 cm signal
arising from the early Universe. Its familiar form disentangles a great deal of
systematic information concerning both the sky and telescope, and displays as a
foreground-dominated `brick' and `wedge' on large line-of-sight scales, and a
complementary `window' on smaller scales. This paper builds on many previous
works in the literature which seek to elucidate the varied instrumental and
foreground factors which contribute to these familiar structures in the 2D
power spectrum. In particular, we consider the effects of $uv$-sampling on the
emergence of the wedge. Our results verify the expectation that arbitrarily
dense instrument layouts in principal restore the missing information that
leads to mode-mixing, and can therefore mitigate the wedge feature. We derive
rule-of-thumb estimates for the required baseline density for complete wedge
mitigation, showing that these will be unachievable in practice. We also
discuss the optimal shape of the layout, showing that logarithmic regularity in
the radial separation of baselines is favourable. While complete suppression of
foreground leakage into the wedge is practically unachievable, we find that
designing layouts which promote radial density and regularity is able to reduce
the amplitude of foreground power by 1-3 orders of magnitude.
