In this paper we discuss a constructive approach to check whether a constant Hamiltonian is Yang-Baxter integrable. We then apply our method to long-range interactions and find the Lax operator and R-matrix of the two-loop SU(2) sector in N=4 SYM. We show that all known integrable long-range deformations of the 6-vertex models of this type can be obtained from a Lax operator and an R-matrix. Finally we discuss what happens at higher loops and highlight some general structures that these models seem to exhibit.Recently, we have started a research direction that focuses on the classification of regular solutions of the quantum Yang-Baxter equation [1,2,3,4,5]. However, from a practical point of view, using our classification to decide whether a Hamiltonian is integrable and descends from an R-matrix is not always very practical. First, there is a lot of freedom in possible identifications and dependence on the spectral parameter. Second, the model under consideration would have to be in the in the set of models that have been classified so far and this is not always obvious.In this paper we try to fill this gap by proposing a constructive method to derive the Lax operator and R-matrix for a Hamiltonian and show whether or not it comes from a regular integrable model. We will demonstrate the method by looking at 6-vertex models, where the situation is under control and very well-understood.Next we focus on a set of integrable spin chains where the existence of a Lax operator and R-matrices are still an open problem. These are the perturbative spin chains that appear in the context of AdS/CFT, see [6] for a review. At one loop, the dilatation operator can be mapped to an integrable nearest neighbour spin chain [7]. However, at each increasing order in perturbation theory, the interaction range of the corresponding spin chain increases [8,9]. Hence, the spin chain Hamiltonian takes the formAt each order of g these spin chains are integrable and the full Hamiltonian would have infinite range.A general frame work for these types of spin chains was put forward in [10,11]. The idea is to introduce a long-range deformation of a nearest neighbour spin chain in a perturbative way. However, this formalism focuses on the level of the charges. Indeed, the idea is to perturbatively introduce long-range deformations of the charges of the system in such a way that they still commute. However, it is unclear if these charges come from a Lax operator and if there is a corresponding solution of the Yang-Baxter equation. In this paper we will show that seems to be the case and we will derive the Lax operator and the R-matrix for the two-loop Hamiltonian in the SU(2) sector of N = 4 SYM.To this end, we will build on the formalism of medium range spin chains studied in [12] and [13]. The idea is to double the local Hilbert space so that the interaction range gets increased. We will find additional evidence for some of the conjectures put forward in [13] in this context.In [14] the perturbative long-range deformation for a general 6-verte...