I tryed just lag bolts (1/2"x6) .I found that if I screwed them in 2" they worked but some came loose, at 3" there was not enough bolt to stand on comfortly and by the end of the season they were all bent
I now use 3/8 x3 1/2" lags to atach steps made out of 6"x6" x3/4 angle iron cut 1 1/2" wide .