The design consists of the visual features of the portions of the blender base shown in solid lines in the drawings, whether those features are features of one of shape, configuration, ornament or pattern or a combination of any of these features. Throughout the Figures, where shown: (i) the dotted lines showing additional structure of the blender base are for illustrative purposes only and form no part of the claimed design; (ii) the unshaded and dotted surfaces do not form part of the claimed design; and (iii) the dotted/dashed lines illustrate unclaimed boundaries of surfaces claimed as part of the design, and form no part of the claimed design. Portions of the blender base not shown in the Figures and not otherwise described in this Specification do not form part of the claimed design.