I cut a massive flowerbed in my garden at the start of this year, I removed all the sods of soil and it took forever, but was worth it in the end. Then, I cut out 6 more beds for my veggies each measuring 10' x 4', and have just laid weed suppressant fabric straight onto the grass between the beds, I have put about 3 inch thickness of bark mulch on top, to act as a path between the beds. I was fed up of cutting the grass between the veggies, as my garden is on a slope and I have a big heavy mower. It is trial and error, I shall have to see if the grass underneath dies back sufficiently. Thirdly I have just laid out a fruit plot, which measures some 50m2, originally I was going to cut rows for my fruit into the grass, but in the end just covered the whole area with weed suppressant fabric, and have cut holes in that for the various fruit shrubs and canes, sinking tubs for the blueberries which are in ericaceous soil. It will again be trial and error over this expanse of grass, as whilst the fabric has been down around 2 weeks, the grass underneath is yellowing now, but I did notice when planting my fruit this last weekend that a few strands of grass have managed to shove their way through the membrane. Whether or not they would continue to grow remains to be seen ....... though hopefully not, as again I covered this area with around 3" thick of bark mulch as per veggie plot. Good luck !