Are Hibernaculums Neccessary for Frogs/Toads or is there an easier smaller alt?

I've got a very small pond that I have had for the past 7 years in my flower bed (sunken in plastic storage box of 45l and replaced this year as it had leaked) that a resident frog/s have spawned since. This summer though due to the heatwave, I didn't see any frogs (or maybe they were hiding in the nooks and crannies in the shaded part of the garden, maybe?) All the pond plants have died and I have replenished the water and bought new elodea for it, but it's very sparse though in the sense there is no cover/protection from potential predators for the frogs should they return to the pond. What shall I do about this, short of buying new plants (made enquiries at a GC but they're not in stock till Spring now)? I've also cleared up the flower bed and most of the garden, but there is a shaded part by the back gate that I can use to make an alt. hidey area for hibernation. I've seen the frog a couple of times but not in the pond.

Whilst researching this online, I've come across a hibernation home for frogs called a hibernaculum

amphibians
Our native amphibians (including species
of newts, frogs and toads) are important
predators, eating a wide variety of pest
insects and are also important prey for
other species. Habitat loss has had an
extremely detrimental affect on amphibian
populations.
Hibernacula are underground chambers that amphibians and reptiles
use through winter to protect them from the cold. You can help to
create hibernacula from piles of rubble, rock, logs and earth banks
(with plenty of mammal burrows and ground fissures) which all make
good hibernation and refuge sites.
Amphibians require humidity and an artificial hibernacula should
ideally be located near to water, but in sheltered habitat (e.g. in long
grass or woodland edge vegetation).
To build the hibernacula, create a mound containing a mixture of
topsoil, rubble, and rough cut logs. Dimensions of the hibernacula
should generally be above 2m length x 1m width x 1m height.
Lay bricks, stones, paving
slabs or large pieces of
concrete over the mound
which will create gaps and
allow amphibians to access
the centre of the mound. Athin
layer of soil and brash, can be
layed over the top of this, as
long as it does not block the
hibernacula access points.
how to build a hibernacula
¶key tips:
how to maintain your hibernacula
¶
¶
Hibernaculas must be free-draining.
Hibernaculas should be located in sheltered areas which are
neither too dry nor prone to winter flooding or freezing (eg in frost
¶
hollows).
Encourage growth of vegetation on the north side of the mound to
provide extra shelter.
To maintain the hibernacula, prevent vegetation from encroaching onto
the south facing side of the mound. Periodic thinning of vegetation on the
hibernacula will help prevent a thick root matt developing, which makes it
hard for reptiles and insects to burrow into the surface. Sparse
vegetation cover on the south facing side of the hibernacula will also give
the animals a suitable location to bask.

I don't really have the space for this, so I'm wondering if a smaller version can be created either on my concrete path or with a tub on its side. Do you this is okay as an alt.?

PS. Over the years, I've never had any problems with returning frogs, so they must find a way of hibernating elsewhere in the garden. I don't think they use the pond as it'll be too cold for them as it's rather deep. (I place a tennis ball to stop it freezing properly)