This study presents the design and development, fabrication, and experimental testing of a four-circular-coil system capable of generating controlled, very low-frequency magnetic fields for biomedical applications. The system is tailored for use with a bioreactor cultivating mesenchymal stem cells, ensuring highly uniform magnetic fields within the area of interest (AOI). An asymptotic approach—the Multiple-Turn Thin-Wire Approximation (MTTWA)—was employed for fast calculations and modeling of multi-turn coil systems with massive windings. The MTTWA-calculated magnetic field distribution of the four-multi-turn coil system was verified with Ansys Maxwell simulations, showing good agreement. The coils and coil system were designed and fabricated, along with a prototype of the exposure system to validate both numerical modeling and simulation results, achieving magnetic field uniformity of at least 97% within the AOI. In the fabricated four-coil exposure setup, symmetric coils are connected in parallel with two separate amplifier-controlled outputs, enabling precise adjustment of field strength, uniformity, and intentional inhomogeneity for specialized experiments. An automated measurement system has been designed and fabricated to measure the magnetic field within the AOI volume with a spatial resolution of 1 mm.