plotting – Put a label near the edge of a Grid object

I have a Grid object and want to put a label near its corner or edge. The label will overlap with the boundary, not fully inside the Grid region. The following example doesn’t work well since the label is partly concealed. Note that I need to work with Grid rather than GraphicsGrid.

plot = Grid[
   Table[Plot[Sin[i x + j [Pi]/3], {x, -[Pi], [Pi]}], {i, 2}, {j, 2}]];
Labeled[plot, "Label", {{Bottom, Right}}, Spacings -> {Automatic, -0.5}]
Labeled[plot, "Label", {{Bottom, Center}}, Spacings -> {Automatic, -0.5}]

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