Como se dice productos hechos por encargo en inglés

Products made to order.

Cakes made to order.

In Dictionaries:

Made to order: Produced or prepared specifically when someone requests the item, so that the item can be customized as desired by the person who requested it. Most fast-food purchases, such as burgers or sandwiches, are made to order; the food has been cooked, and items are warm, but the final product is not assembled until the customer has actually ordered it. This way, if the customer has any special requests, the staff is able to accommodate them. As another example, a woman could purchase a made to order dress; this dress would be sewn to the size she requests, and would use the fabric and pattern she desired. Also called build to order.
 Business Dictionary.

In News:

"Roth’s Vista Market has added a quick, tasty and convenient option: made-to-order burgers at a grill station near the deli department."
Statesman Journal.

Como se dice trabajo a destajo en inglés

Piecework.

Piecework: work for which the amount of pay depends on the number of things finished rather than the time spent making them.
Cambridge Dictionary Online.

Piecework:  work in which you are paid for each thing you make or do and not for the amount of time you work
Merriam Webster Dictionary.

Tener sello húmedo (un documento)

To get/have the rubber-stamp.

"Your application should get the rubber stamp from the residents' association."
Oxford Advanced Dictionary.