We’re not going to lie, assembling the Wellingtons can be tricky—but all you truly need is a little patience and this step-by-step guide.
Form vegetable mixture on bottom half of puff pastry into a tightly packed 3×8-in. rectangle, leaving a 1-in. border around edges.
Arrange two squash halves flat-side down, with tapered ends facing out, over rice mixture on each pastry. Trim squash if needed.
Fold top half of pastry over squash, stretching gently to cover. Press edges together to close, then press with tines of a fork to seal.