With the help of a friend, position the ledger against the flashing so the top edge is in line with its corresponding marking on the flashing. Tack the ledger board in place for now using a 2 ½” spiral nail. Do not pound the nail entirely. Check for level across the length of the ledger board.
Mark the positions where the joists will go along the ledger board. Ideally, they should be in line with the floor joists for simplicity.
Using a ½” spade bit bore at least two holes through the ledger board, one above each other, between each joist. The number of bolts required depends upon the expected load on the deck. Bore through the ledger and right through the rim joist and into the blocking.
To be safe, do not be afraid to put four bolts between each set of joists—two bolts top and bottom on the left and right side of each joist.
Now pry the ledger board away from the flashing. Then you can check to see if you are bored through the blocking by looking from inside the basement.
If not, drill again and complete the bore. Cut a notch for any obstacles like a gas line.
Place ½” bolts into each hole in the ledger board. Use washers under each nut's head and ideally (but not essential) two washers on the backside of the bolt to create a small air space between the ledger and the first flashing.
Water should never get back here, but if it ever does, it has a means of egress keeping the ledger from ever rotting.
With the help of a friend, re-position the ledger bo. Line up the bolts into the holes and push them through the blocking. Screw the nuts with washers from the basement side and tighten up the connections.