Ultrablack surfaces are vital in thermal radiation and other fields. This study introduces a cost-effective method to create ultrablack surfaces with broad spectral and high absorption traits using femtosecond laser and reverse molding technology. It investigates the impact of laser parameters on the morphology and size of copper surface microstructures, determining optimal parameters for periodic microstructure processing. The research develops a process flow that integrates secondary molds with black paint substrates, achieving a flexible ultrablack surface with high absorption across the solar spectrum. An innovative solar absorber design using the ultrablack surface and ITO transparent glass is tested through outdoor experiments. The results demonstrate absorption rates of up to 98.3% for normal incidence and over 90% at a 70° angle. The solar absorber with ITO glass can increase the device temperature by up to 4 ℃. The process is simple, cost-effective, and suitable for large-scale application due to its flexible substrate.