Starting a patch from scratch

Ok - I've finished the raspberry patch and I will do this! 

I need advice

It needs to be as low maintenance as possible - I have the garden to look after but I really want to do this.

The area is 30ft x14ft - grassed. There are trees nearby so it does have roots underground - but no other options. 

How would you tackle this. 
I would like to go no dig? I ave weed membrane - and more wood chips than you can imagine. A small amount of compost, manure and lots of card

Can I just cover with card and go for it ....

What do you want to grow there?

The way the weather is just now I would cover with cardboard, but only cover enough that you can weigh down straight away with either compost or woodchip. Like veggie says, what you are going to grow there dictates how you will treat it.

Flowers.

Is it flowers in the Random scattered sense, or orderly rows for picking sense? I'm guessing the latter.
Do you want it to look pretty or functional?
Are they annuals or perennials?
Seed sown or planted as plugs?

In my simple mind, you treat the patch the same as you would growing veg.

Wouldn't use weed membrane, after a time it starts to unravel and you get lots of thin bits of plastic turning up all over the garden, and the more we can garden without plastic the better, I would use the membrane under paths or paving, sealing the edges with a bit of light heat from a weed burner, I would suggest that you spread a good layer of wood chipover the area scatter some chicken pellets or manure through it then cover with several layers of cardboard and newspapers, the question is what do you have to cover that with, and if you have anything could it give you 5 or 6 inches of cover, if not I would purchase 2 builders bags of washed course sand, add any soil that you have and if required several bags of the cheapest compost I could find, mix it through the sand (basicly to hold moisture) as you spread the sand over the area, again scatter chicken pellets across the bed, might be a good idea if you could make a frame around the edges, till the bed settles, but not a must have thing, a bed of course sand could be used to hold pots for the first year, then after that it could be planted out as normal

I wouldn't use membrane either. Just get cardboard, and cover it with one or two inches of compost or manure, whatever you have. That's it. Sow or plant into it

I did that on a grassy patch around the summer house and planted my garlic there. Thick card, horse manure, garlic straight in. They're about 10cm tall now. The only weeds are in the corners so far.

I will use that method in every place I can in the garden where I will grow veggies or flowers, whether from seed, seedlings or fully grown plants.

I imagine you are going to have rows of flowers to cut with paths between? If so, cover the whole lot with cardboard and use woodchip on the paths and compost on the beds!  Simples!

I'm another one picking bits of plastic from broken down weed membrane out of my garden - and that is just what has gone under paths and gravel, but still after a decade it has started to distintegrate.
Cardboard and manure or compost would be my way forward, too. If you have time/energy space you could lift the turves, stack and make loam if you think you might need soil elsewhere, but it's probably best just broken down in situe.
I am a fan of grass paths, I like the look, they have lots of flowers in them (I know, weeds!) but i do have the time to cut them. If starting today I probably would just use chippings for paths!

The area is 30ft x14ft - grassed. There are trees nearby so it does have roots underground - but no other options. 

How would you tackle this. 
I would like to go no dig? I ave weed membrane - and more wood chips than you can imagine. A small amount of compost, manure and lots of card

Can I just cover with card and go for it ....

 I'd divide it in two - two 14' square beds with a 2' foot-ish path across the middle. Then grow your flowers in 14' long rows, in whichever direction works best for light and access.