This study presents a pioneering advancement in the application of Direct Laser Interference Patterning (DLIP) by integrating it with a high-power, multimode nanosecond fiber laser based on an innovative technology called Extended Laser Interference Patterning System (ELIPSYS®, SurFunction GmbH). This configuration demonstrated the ability to create well-defined interference patterns with a periodicity of 24 µm over a deep focus range of approximately 0.6 mm, making it suitable for large-area surface microprocessing. The influence of laser parameters, particularly pulse energy (E_p) and pulse-to-pulse overlap (O_p), on the depth and quality of the laser-produced structures is investigated. By taking into consideration both structure depth and its variation across the patterned area, an optimal process window for superior structure quality is identified. Considering a relative deviation lower than 15 % in the structure depth, periodic structures with a 24.0 µm spatial period and depths from ∼1.0 µm to 18.7 µm could be fabricated with pulse overlaps from ∼60 % to 95 % and pulse energies from 20 mJ to 50 mJ.