There is no sharp low and no single dramatic bar. Price decelerates, drifts sideways, and then gradually turns up, often with volume heaviest at the start and end of the curve and lightest in the middle.
Rounding bottoms are associated with accumulation: they take a long time precisely because inventory is changing hands slowly without moving the price. The pattern completes when price breaks above the left side of the bowl.
They are frustrating to trade because there is no clean invalidation-level, the curve is drawn by eye, and the base can extend for far longer than expected. Most traders wait for the breakout rather than trying to buy the curve, accepting a worse price for a definable risk.
Related: cup-and-handle, accumulation, double-bottom, consolidation, volume-dry-up