Keep both hands on the tool using your non-dominant hand as a brake. This does two things, first you can't cut yourself if both hands are behind the blade. Second the brake hand which pulls back while the other hand pushes, will give you much better control against slips. Get or make a "bench hook" which is a board with a stop or cleat on both the top and bottom. the bottom cleat hooks over the edge of the table and anchors the board and the top cleat acts as a stop for what you're cutting. No need to hold the lino with your hand.