Wooden shelter on bricks

Hi, I have just laid two courses of bricks ready to build a summerhouse/garden shelter on. Its only three sided, with the front open for access.

I have the frogs up, so before i put the shed on i'm going to lay a mortar course, so the timber can sit level. Going to do about 10mm course in sharp sand, and 4:1, is this ok?

Would i need a DPC here, or will it be detrimental? If so, is it a case of lay mortar to fill frogs, press the DPC into the mortar, then lay 10mm on top of the DPC? The timber is going to be screwed to the mortar then, will probably put a bit of silicone on the screw thread to seal again, though I have heard theres no need, but it wont hurt will it?

Thanks

Ok this is how I do it, I have built several timber outbuildings over the years.
Build the floor frame to the size of the building you require.
Get a supply of concrete block and put one on each corner layed flat or two on top of each other if you need more height and level the floor up adding more blocks were you think it needs more support. The more block supports the stronger the floor will be. I always put a bit of slate between the blocks and the timber to stop any rising damp. Then I knock some steel in the ground at each corner as deep as I can then I drill it to my floor joists to stop it moving in strong winds. Then you can lay some timber around the edge of the floor joists to act as your wall plate and nail it in position, across the sides that don't cross the joists every 18" or so the you could add a few noggins to support the wall plate on those sides. Old flags are also good for supporting your joists.

Thanks for the info, but I've already put the concrete base in and the first two courses of bricks

Staple the dpc to the underside of the frame where it comes into contact with the mortar bed.

Air flow under the structure is important for timber.