A method for fracking a hydrocarbon formation. An actuating member, flowable along a production string, is provided. A unique key portion thereon engages a desired sliding sleeve covering an associated port in the production string. Applying uphole fluid pressure causes the sliding sleeve and actuating member to move so as to uncover the associated port. After fracking and cessation of supply of pressurized fracturing fluid, a compressed spring on the actuating member decompresses so as to reposition a sand screen immediately beneath the port so as to prevent sand from flowing into the production string. Flowable insertion of additional “keyed” actuating members allows similar opening of additional successive uphole ports and fracking in the regions of such additional opened ports, with similar location of sand screens at each opened port. Plug members on each actuating member thereafter dissolve or are successively burst to thereby allow production.