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Further to Andrew's excellent advice, Google found these using 'leg
elevation leg ulcers'.

Leg elevation encourages venous return and may reduce pain and leg swelling
[Royal College of Nursing, 2000a]. Raising the legs above hip level for 30
minutes three to four times a day will allow swelling to subside and improve
microcirculation in people with venous insufficiency. Placing several
pillows under the bed mattress will assist leg elevation at night. However,
there is insufficient evidence to recommend regular leg elevation as a
routine intervention.

Source: http://www.prodigy.nhs.uk/guidance.asp?gt=Leg%20ulcer%20-%20venous

Elevation and activity

When you are resting, if possible, try and keep your leg elevated (raised)
higher than your hip. This is particularly important if your leg is swollen.
The aim is to let gravity help to pull fluid and blood in the right
direction - towards the heart. This reduces swelling in the leg, and reduces
the pressure of blood in the leg veins.

Try to set 3 or 4 periods per day of about 30 minutes to lie down with your
leg raised. For example, lie on a bed or sofa with your foot on a couple of
pillows. However, do not spend all your time in bed or resting. For the rest
of the time, keep as active as you can, and do normal activities. If
possible, regular walks are good, but do not stand for long periods.

When you sleep overnight, if possible, try to keep your leg raised. You can
do this by putting some pillows under the bottom of the mattress. (It may
not be possible to sleep like this if you have certain other medical
problems or disabilities.)

Source: http://www.patient.co.uk/showdoc/23068777/

The higher the leg, the lower the pressure in the leg veins! If the foot is
elevated above the heart then the pressure in the foot drops to a normal
level. Put your legs up whenever you can and as high as you are able-the arm
of the sofa is good. Elevate the lower end of your bed (6 inches or so) so
that when in bed your feet are a little higher than your head. You can use
some old books for this.

Source; http://www.vascularsociety.org.uk/patient/legulcer.html

I don't understand why the doctor(s) or nurse(s) looking after your relative
haven't advised on this aspect of care. In my experience, patients can only
tolerate leg elevation for short periods when sitting because of the
discomfort caused by the hip joint being flexed. Elevating the lower leg
above the level of the heart, even when lying in bed, is neither practical
nor well tolerated!

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Reduced mobility and "other complaints" are factors that can delay wound
healing. If your relative is elderly, then advanced age is another factor
that can delay wound healing. You say that your relative is overweight; it
can still be the case that an overweight person has some nutritional
deficiences which can include a deficit in the essential factors needed for
wound healing, such as proteins, vitamins and minerals. Nutritional
assessment can determine this, and from that attempts can be made to correct
any nutritional deficiences. As Andrew says, a full assessment is needed.
Obviously I don't know the full circumstances but in a worse-case scenario
it is possible that complete healing of both these ulcers is not a realistic
goal in this particular case. I hope that isn't the case!

The local Occupational Therapists should have access to a variety of
devices to help.  For "made to measure" solutions try contacting your
local REMAP Panel (www.remap.org.uk).