The use of Al2O3 as reinforcement in aluminum matrix composites (AMCs) allows good interface wetting with the aluminum alloy matrix, thereby improving their mechanical property. However, the uniform mixing of Al2O3 reinforcement particles using a general stir casting method is a challenge, specifically at higher concentrations. Process modification using mechanical stirring along with sonication under specific environment can solve this issue and avoiding use of any dispersants/additives. This work discuss on parameters optimization (as stir speed, stir time, particle and ingot preheating temperatures, using different methods of reinforcement addition in melt, melt temperature, heating cycle, pouring temperature and mold temperature) and process modifications (use of vacuum casting, argon casting, and ultrasonic-assisted casting) in a bottom pouring stir casting process to ensure homogeneous mixing and uniform distribution of reinforcement in the metal matrix. A 1wt% Al2O3–Al6061 composite is prepared using the bottom pouring stir casting method under three different process conditions: vacuum casting, argon casting, and ultrasonic-assisted vacuum casting methods. Challenges such as inadequate mixing, wettability, high porosity, and non-homogeneous distribution of micron-size aluminum oxide (Al2O3) particle reinforcement have been addressed. The results show improved mixing of Al2O3 particles in the aluminum matrix using ultrasonic-assisted vacuum casting technique. An improvement in hardness of the composite is observed from 55 to 60 HV with the ultrasonic-assisted vacuum casting method.