Laser welding has become increasingly popular in recent decades due to its high processing speed and minimal heat-affected zone, which contribute to extended component lifetimes. However, the adoption of this advanced technique is often hindered by a lack of skilled personnel associated with traditional welding and limited awareness of its potential. This study proposes a straightforward methodology for developing a finite element-based thermal model for laser welding, incorporating a two-step experimental calibration process. Using temperature measurements from thermocouples and data from a welding spot test, the numerical model was calibrated to optimize combinations of welding speed and power. The study focuses on S275JR structural steel, involving initial spot weld followed by a linear welding trajectory. The results demonstrate the precision of the proposed calibration approach, as numerical predictions closely align with experimental data from all three thermocouples. The findings validate the effectiveness and accuracy of this methodology, highlighting its ability to adapt spot calibration results to more complex linear welding scenarios. Moreover, the simplicity of the process ensures it is accessible and broadly applicable across different materials and welding configurations. This work offers a reliable and resource-efficient framework for laser welding process optimization in industrial applications.