A guiding pattern for directed self-assembly (DSA) of a block copolymer (BCP) is an array of spaced guiding stripes on a substrate that have a width equal to nL0 and a pitch equal to (n+k)L0, where n and k are integers equal to or greater than 1 and L0 is the natural pitch of the BCP. The guiding stripes have oxidized sidewalls. A silicon-containing BCP self-assembles with the BCP component without silicon wetting the oxidized sidewalls. Then oxygen reactive ion etching (RIE) removes the BCP component without silicon and oxidizes the silicon-containing BCP component. The remaining pattern of silicon oxide containing BCP component can then be used as an etch mask to etch the underlying substrate.