Endoscopic resection with transnasal craniectomy (ERTC) and skull-base reconstruction (SBR) are effective techniques for sinonasal/skull-base malignancies treatment. Endoscopic endonasal SBR techniques are mainly based on homologue-free grafts with excellent outcomes, but alternative techniques can be used such as regional vascularized pedicled flaps or local pedicled flap-like Hadad-Bassagasteguy nasoseptal flap and the septal flip flap (SFF). The purpose of this article is to describe an inferiorly based septal flap aimed to promote mucosal healing and improve patients' quality of life. We reported a clinical case of 51-year-old female affected by olfactory neuroblastoma, Hyams-Ⅱ, Kadish-INSICA-B treated with unilateral ERTC and SBR with fascia lata, SFF, and modified reverse septal flap (mRSF). The mRSF harvesting is described in detail, to obtain a lower hinged flap with random vascularization, which can be rotated to cover the exposed bone of the nasal cavity floor. Endoscopic evaluations immediately showed rapid healing with a minimal amount of nasal crusting, despite the adjuvant treatment and the short time since the surgery. This surgical technique is a simple and viable way to boost nasal healing after endoscopic endonasal surgery and for nasal floor resurfacing after septal removal following a unilateral ERTC.