A method for synthesizing a target double stranded (ds) polynucleotide having a predefined sequence, comprising a) providing an oligonucleotide library within an array device, which comprises a diversity of oligonucleotide library members, wherein each of the library members has a different nucleotide sequence and is contained in a separate library containment in an aqueous solution, wherein the library members are pre-built in storage stable solutions, and located in separate library containments at defined positions within the array device which are spatially arranged in a three-dimensional order at defined coordinates within the x-, y-and z-axes, which diversity includes single stranded oligonucleotides (ss oligos) with a length of 6 to 26 nt, and double stranded oligonucleotides (ds oligos) with a length of 6 to 26 bp and at least one overhang that is not more than half of the respective ds oligo length, and which diversity covers at least 10.000 pairs of matching oligonucleotides; b) in a first step, transferring a first pair of matching oligonucleotides from said library into a first reaction containment using a liquid handler and assembling said pair of matching oligonucleotides thereby obtaining a first reaction product comprising at least one overhang; c) in a second and further steps, transferring a second and further pairs of matching oligonucleotides from said library into a second and further reaction containments, respectively, using a liquid handler and assembling said pairs of matching oligonucleotides thereby obtaining a second and further reaction products each comprising at least one overhang, respectively, d) assembling said first, second and further reaction products in a predetermined hierarchical assembly workflow, thereby producing said target ds polynucleotide with an overhang, optionally followed by a finalization step to prepare blunt ends; wherein said pairs of matching oligonucleotides used in step b) and c) and said hierarchical assembly workflow are determined using an algorithm to produce said target ds polynucleotide; wherein a pair of matching ss oligos consists of two ss oligos with partially complimentary sequences, and a pair of matching ds oligos consists of two ds oligos with complementary sequences in the respective overhangs of the ds oligos; and wherein a series of different target ds polynucleotides having a length of at least 1.000 bp and a sequence identity of less than 50% are synthesized using the same oligonucleotide library. a) providing an oligonucleotide library within an array device, which comprises a diversity of oligonucleotide library members, wherein each of the library members has a different nucleotide sequence and is contained in a separate library containment in an aqueous solution, wherein the library members are pre-built in storage stable solutions, and located in separate library containments at defined positions within the array device which are spatially arranged in a three-dimensional order at defined coordinates within the x-, y-and z-axes, which diversity includes single stranded oligonucleotides (ss oligos) with a length of 6 to 26 nt, and double stranded oligonucleotides (ds oligos) with a length of 6 to 26 bp and at least one overhang that is not more than half of the respective ds oligo length, and which diversity covers at least 10.000 pairs of matching oligonucleotides; b) in a first step, transferring a first pair of matching oligonucleotides from said library into a first reaction containment using a liquid handler and assembling said pair of matching oligonucleotides thereby obtaining a first reaction product comprising at least one overhang; c) in a second and further steps, transferring a second and further pairs of matching oligonucleotides from said library into a second and further reaction containments, respectively, using a liquid handler and assembling said pairs of matching oligonucleotides thereby obtaining a second and further reaction products each comprising at least one overhang, respectively, d) assembling said first, second and further reaction products in a predetermined hierarchical assembly workflow, thereby producing said target ds polynucleotide with an overhang, optionally followed by a finalization step to prepare blunt ends; wherein said pairs of matching oligonucleotides used in step b) and c) and said hierarchical assembly workflow are determined using an algorithm to produce said target ds polynucleotide; wherein a pair of matching ss oligos consists of two ss oligos with partially complimentary sequences, and a pair of matching ds oligos consists of two ds oligos with complementary sequences in the respective overhangs of the ds oligos; and wherein a series of different target ds polynucleotides having a length of at least 1.000 bp and a sequence identity of less than 50% are synthesized using the same oligonucleotide library.