<xsl:apply-templates select="a"/>

         <container1>
           <xsl:copy-of select="b|c"/>
         </container1>

<xsl:apply-templates select="d|e|f"/>

         <container2>
           <xsl:copy-of select="g|h|i"/>
         </container2>

<xsl:apply-templates select="j"/>

it does not preserve the original order of the elements but
collects together all elements in each group. That isn't what i
understood you to want, but if that is what you want, you don't need any
grouping construct at all.