I have rapacious weeds as well as finding it impossible to keep my flying chickens off the veg patch, so I sow my leek seedlings in pots, then plant them out into the deep broomhandle holes once they are about 6" tall - you can cram a lot into one pot. I am very late this year so I will probably plant them closer and use them as baby veg instead of expecting them to survive the winter.
Having sown your outdoors, you will have to move them on in about July or they won't have room to develop.
Interesting you are trying the seed shallots ellied. I have grown them three times now - first time swamped with chickweed, second time not worth it, third time in the tunnel with careful weeding crop ok but not exceptional - quite fiddly little bulbs. Haven't sown any this year but I will be interested to hear how yours go.