Get him to think about what he will use the garden for, will he be sitting in it to chill after work, having friends over to bbq, does he cook and need herbs, does he want to encourage wildlife, eg birds, insects. Does he needs a table, how big, what style, what materials, urban chic or pub garden? Is there an outside tap? Having easy access to water makes a difference in keeping plants alive for a lazy gardener
,if no tap can he invest in a water butt?
I would forget about a lawn, it’s a small area but would still need regular cutting and edging, requiring tools needing storage. Paving would be the answer, but it’s important not to pave the whole area, there needs to be drainage so some open space/soil for surface water to soak away naturally is essential.
I honk he needs to think about having some different levels, to break up the space visually, this would be hard to achieve by landscaping and shifting soil, but you can do a lot with raised beds (really raised, say 40 cm, )or raised seating areas .
I would look at getting interesting pots that can be arranged in groups, lots of perennial plants grow well in pots or he could fill them with cheap annuals from the garden centre for seasonal interest.
In terms of plants he needs fool proof things that have strong lines and both look after themselves and have year round , or as near as damn it interest eg Fatsia japonica, standard bay tree, standard olive, figs, New Zealand flax, rosemary, lavender, winter box. All fine in pots, but they will be in them for a while so plant in decent compost like a John innes.
Does he know which fence is his? I think he could grow fan or cordon apples or pears, not too difficult and look striking.