Former Liverpool ace joins Llangefni Town.
Boersma is assistant to newly-appointed player-manager Alex Kevan. They will be in charge of Llangefni's team for tomorrow's match against Porthmadog at the Traeth (2.30pm).
These teams met at Llangefni on Saturday when Porthmadog emerged 4-1 winners.
Boersma spent much of his coaching career working with ex-Reds club-mate Graeme Souness at Rangers, Liverpool, Southampton, Blackburn Rovers and Newcastle.
Kevan is also set to sign former Caernarfon Town midfielder Paul Roberts and ex-Liverpool man Chris O'Brien as soon as the transfer window opens tomorrow.
Caersws, who play Newtown at Latham Park tomorrow, are keen to sign defenders Kevin Scott and Mike Parry. Llanelli are in contract talks with striker Rhys Griffiths to ensure Swiss club FC FC Aarau can't sign him on a Bosman free at the end of the season.
Griffiths' current deal ends this summer and Aarau are keen on the striker who has led the Welsh goalscoring charts for the last two seasons.
Tomorrow, Llanelli play Carmarthen Town at Stebonheath Park (2.30pm), having beaten the same opposition 2-1 away on Saturday. Neath Athletic and Port Talbot Town clash at Llandarcy Park tomorrow, having drawn 3-3 at the Re/Max Stadium last weekend.
TNS take on Welshpool Town tomorrow (2.30pm). Welshpool host Cardiff in the FAW Premier Cup on January 8.