out=x:

convert -size 420x230 xc:white \
    -stroke black -fill darkgray -draw 'rectangle 20,20 400,200' \
    +stroke       -fill black -gravity north -annotate +0+25 'border' \
    -stroke black -fill lightgray -draw 'rectangle 40,40 380,180' \
    +stroke       -fill black -gravity north -annotate +0+50 'padding' \
    -stroke black -fill white -draw 'rectangle 70,70 350,150' \
    +stroke       -fill black -gravity north -annotate +0+80 'content' \
    -draw 'line 70,210 70,220' \
    -draw 'line 70,215 190,215' \
    -draw 'line 230,215 350,215' \
    -draw 'line 350,210 350,220' \
    -annotate +0+210 'width' \
    "$out"