Yes, it is advisable to allocate separate time for building a strong foundation in concepts and for honing answer writing skills in your PSIR study plan. This is because:

1. Building a strong foundation in concepts:
- Understanding the concepts is essential for a comprehensive understanding of the subject. It helps in developing a holistic perspective and analytical skills.
- PSIR is a subject that requires a deep understanding of political science theories, international relations, and Indian politics. Therefore, allocating time for concept-building is crucial.
- It involves reading textbooks, reference books, and scholarly articles to grasp the theoretical frameworks and ideas.
- It also requires critical thinking and analysis to relate the concepts to real-world scenarios and events.

2. Honing answer writing skills:
- Answer writing is a crucial aspect of the UPSC examination. It tests the candidate's ability to articulate their knowledge and present arguments effectively.
- Allocating separate time for answer writing practice helps in enhancing writing speed, time management, and structuring the answers properly.
- It allows you to practice different types of questions, such as essay-type questions, short answer questions, and case studies, which are commonly asked in the exam.
- Regular practice also helps in identifying your weaknesses, improving content presentation, and developing a coherent and logical writing style.

3. Balancing concept-building and answer writing:
- While building a strong foundation in concepts is important, solely focusing on it may lead to neglecting the answer writing skills, which are equally important for scoring well in the exam.
- Allocating separate time for both aspects ensures a well-rounded preparation strategy.
- You can dedicate specific days or hours for concept-building, where you focus on reading and understanding the subject matter deeply.
- On other days, you can practice answer writing by attempting previous year question papers, mock tests, and sample papers. This will help you apply the knowledge gained from concept-building in a structured manner.

In conclusion, allocating separate time for building a strong foundation in concepts and honing answer writing skills is advisable in your PSIR study plan. It ensures a comprehensive understanding of the subject and enhances your ability to present your knowledge effectively in the examination.