The most critical clue on the board was the single Red square in the top-left corner. Clues without numbers have unknown areas, but their placement is key. Being in a corner, and given the surrounding clues, its most logical and constrained shape is a square. The solution confirms it's a 3x3 square (Area 9). Placing this piece first is the optimal move, as it immediately defines a large, predictable border for its neighbors.

With the 3x3 Red square in place, its right edge creates a solid wall. The Green '3' clue is positioned directly in the narrow channel between this new wall and the piece to its right. A shape of Area 3 can only be a 1x3 or a 3x1 rectangle. Since the channel is only one cell wide, the Green piece is forced into a 1x3 vertical orientation. There was no other possibility.

The solved Red and Green shapes now form a hard boundary for the Light Blue clue. Boxed in from the left and below, and by the grid's top edge, its dimensions become clear. It resolves into a 3x2 rectangle (Area 6). This placement, in turn, dictates the space available for the Purple '3' clue directly beneath it, forcing it into a 3x1 horizontal strip.

like the Red square, the Brown clue in the bottom-left corner serves as a second anchor. By placing it as a 3x2 rectangle, it neatly fills the corner and creates clean boundaries for the cluster of clues in the middle, setting up the puzzle's endgame.

With the large anchor pieces in place, the rest of the grid becomes a simple matter of fitting the remaining numbered clues (all Area 3) into the defined spaces. Each placement resolved the ambiguity for the next, demonstrating how a good start converts a complex grid into a series of simple decisions.