"生拼硬凑地写出" can be translated into English as "to piece together (something) in a forced or haphazard manner" or "to cobble together (a text, story, etc.)".
For a more literal and context-specific translation in a writing context, you might say:
"To write (something) by forcefully piecing unrelated parts together."
"To compose (something) in a makeshift and unnatural way."
However, the most concise and commonly used expressions would likely be:
"To cobble together a piece of writing."
"To forcefully piece together a text."
Choose the phrase that best fits the context and tone you're aiming for.