Pieceword

With the help of the Across clues only, can you fit the 25 pieces into their correct positions in the empty grid (which, when completed, will exhibit a symmetrical pattern)?

ACROSS

1 Keep-fit activity • Treacle 3 Cuffed • Sour taste 5 Void, non-existent • Forcibly influence, mentally 7 Hoisted • Marine gastropod which clings to rocks 9 Inconsistent • Denigrate 11 Quality • Suddenly flaring star 13 Hindered • As a result 15 Duck whose feathers are used in quilts • Boring, dull