Shear strength is a measure of soil strength characterized by the effective cohesion (c, kPa) and the internal friction angle (φ, degrees). For sandy clay soils, the determination of shear strength through traditional laboratory tests such as shear or compression on undisturbed soil samples is currently not feasible, as obtaining standard-size undisturbed samples of sandy clay soils has not yet been accomplished. Therefore, the shear strength for this type of soil is typically assessed using shear tests on reconstituted soil samples of specific density, with large dimensions ranging from 200 × 200 to 500 × 500 mm. This study involves the design and fabrication of a sampling kit for undisturbed cylindrical samples of sandy clay with a diameter of D_sample = 152 mm and a height of H_sample = 200 mm. The apparatus consists of three main components, constructed from CT3 and C45 steel. Field testing results enable the extraction of undisturbed soil samples from sandy clay with a maximum particle size of up to 19.0 mm, with the samples exhibiting a range of consistency from plastic to hard. The findings of this research provide a foundational framework for developing equipment for flat shear testing of undisturbed sandy clay samples in the laboratory in the near future.