China Low Activation Martensitic (CLAM) steel has been developed at Institute of Nuclear Energy Safety Technology under wide collaboration. Fabrication techniques for test blanket modules (TBMs) are being developed, and a 1/3 scale prototype is being fabricated. A 1/3 scale first wall (FW) mockup was fabricated by a one-step hot isostatic pressing (HIP) method with CLAM steel rectangular tubes and plates. Two cover plates and type L cooling plates were produced with strips and grooved plates using electron beam welding (EB) and HIP diffusion bonding. Also, the assembly routine of the FW cover plates and cooling plates and four back plates were pre-tested using solid plates. And, the FW, cooling plate and cover plates were non-destructively tested using dimensional measurements and ultrasonic wave tests, which showed preliminarily the feasibility of the fabrication process.