It is so-called turn footwear: the sole was sewn to the boot from inside, the boot’s inside was wetted with water and turned out.
Such high boots with broad tops were homemade from embossed cowhide or seal skin, sewing it together with wax-ends, i.e. strong tarred or waxed linen thread; pull straps were sewn to the tops and caps; the heel was hobnailed. For higher strength and moisture protection, the waders were greased with tar and fish-oil, and soaked in salted water. The Pomors used the waders not only as fishing footwear but also as everyday and winter footwear.
Abstract by O.G. Baranova