An example of the reconstructed signal (predictive posterior of the final function given the distribution of the parameter posteriors) using a six-knot FlexKnot signal model with neither prior constraint on the first knot nor the theoretical dark ages primer (theoretical global 21-cm signal values within the dark ages frequencies). The red-dashed line represents the simulated injected signal. The reconstructed signal in blue contours diverges at the lower frequency end, otherwise being reasonably well recovered, such as the centre frequency, absorption level, and width.