A method of forming a three-dimensional object, comprising: providing a carrier and an optically transparent member having a build surface, said carrier and said build surface defining a build region therebetween; filling said build region with a polymerizable liquid; continuously or intermittently irradiating said build region with light through said optically transparent member to form a solid polymer from said polymerizable liquid; continuously or intermittently advancing, e.g. sequentially or concurrently with said irradiating step, said carrier away from said build surface to form said three-dimensional object from said solid polymer; wherein said optically transparent member comprises a build plate comprising: an optically transparent first channel layer; an optically transparent second channel layer on the first channel layer; and a flexible, optically transparent sheet having an upper and lower surface, the sheet upper surface comprising a build surface for forming a three-dimensional object, the sheet lower surface being positioned on the second channel layer; further comprising applying a reduced pressure and/or polymer inhibitor-enriched gas to the polymerizable liquid through the second channel layer and the optically transparent member to thereby reduce a gas content of the polymerizable liquid; and wherein the step of applying a reduced pressure and/or polymer inhibitor-enriched gas either comprises supplying a polymerization inhibitor gas to the polymerizable liquid at a substantially constant pressure, or comprises intermittently applying a reduced pressure. providing a carrier and an optically transparent member having a build surface, said carrier and said build surface defining a build region therebetween; filling said build region with a polymerizable liquid; continuously or intermittently irradiating said build region with light through said optically transparent member to form a solid polymer from said polymerizable liquid; continuously or intermittently advancing, e.g. sequentially or concurrently with said irradiating step, said carrier away from said build surface to form said three-dimensional object from said solid polymer; wherein said optically transparent member comprises a build plate comprising: an optically transparent first channel layer; an optically transparent second channel layer on the first channel layer; and a flexible, optically transparent sheet having an upper and lower surface, an optically transparent first channel layer; an optically transparent second channel layer on the first channel layer; and a flexible, optically transparent sheet having an upper and lower surface, the sheet upper surface comprising a build surface for forming a three-dimensional object, the sheet lower surface being positioned on the second channel layer; further comprising applying a reduced pressure and/or polymer inhibitor-enriched gas to the polymerizable liquid through the second channel layer and the optically transparent member to thereby reduce a gas content of the polymerizable liquid; and wherein the step of applying a reduced pressure and/or polymer inhibitor-enriched gas either comprises supplying a polymerization inhibitor gas to the polymerizable liquid at a substantially constant pressure, or comprises intermittently applying a reduced pressure.