\tikzstyle{anaflowbox} = [ draw=black
                         , text width=2.7cm
                         , minimum size=1.2cm
                         , align=center
                         , rounded corners
                         , thick
                         , fill=lightgray
                         , font=\Large
                         ]

\node[anaflowbox] (schematic) at (0,0) {Schematic};

\node[anchor=east] (circuit) at (schematic.west) {
 \smartdiagram[sequence diagram]{Circuit Design}
};

\node[anchor=west] (layout) at (schematic.east) {
 \smartdiagram[sequence diagram]{Layout Design}
};

\node[anaflowbox, anchor=west] at (layout.east) {Layout};

\node[anaflowbox, anchor=east] at (circuit.west) {Specification};